Removed JAVA_HOME using only LS_JAVA_HOME

Updated all the Logstash launching scripts to use only LS_JAVA_HOME as environment variable to
determine the JDK to use to launch Logstash. JAVA_HOME is abandoned for this job.

bin/logstash.lib.sh

@@ -14,8 +14,7 @@
 # The following env var will be used by this script if set:
 #   LS_GEM_HOME and LS_GEM_PATH to overwrite the path assigned to GEM_HOME and GEM_PATH
 #   LS_JAVA_OPTS to append extra options to the JVM options provided by logstash
-#   LS_JAVA_HOME to point to the java home (takes precedence over JAVA_HOME)
-#   (deprecated) JAVA_HOME to point to the java home
+#   LS_JAVA_HOME to point to the java home
 
 unset CDPATH
 # This unwieldy bit of scripting is to try to catch instances where Logstash
@@ -101,17 +100,6 @@ setup_java() {
       else
         echo "Invalid LS_JAVA_HOME, doesn't contain bin/java executable."
       fi
-    elif [ -n "$JAVA_HOME" ]; then
-      echo "Using JAVA_HOME defined java: ${JAVA_HOME}"
-      if [ -x "$JAVA_HOME/bin/java" ]; then
-        JAVACMD="$JAVA_HOME/bin/java"
-        if [ -d "${LOGSTASH_HOME}/${BUNDLED_JDK_PART}" -a -x "${LOGSTASH_HOME}/${BUNDLED_JDK_PART}/bin/java" ]; then
-          echo "WARNING: Using JAVA_HOME while Logstash distribution comes with a bundled JDK."
-        fi
-      else
-        echo "Invalid JAVA_HOME, doesn't contain bin/java executable."
-      fi
-      echo "DEPRECATION: The use of JAVA_HOME is now deprecated and will be removed starting from 8.0. Please configure LS_JAVA_HOME instead."
     elif [ -d "${LOGSTASH_HOME}/${BUNDLED_JDK_PART}" -a -x "${LOGSTASH_HOME}/${BUNDLED_JDK_PART}/bin/java" ]; then
       echo "Using bundled JDK: ${LOGSTASH_HOME}/${BUNDLED_JDK_PART}"
       JAVACMD="${LOGSTASH_HOME}/${BUNDLED_JDK_PART}/bin/java"

bin/setup.bat

@@ -26,13 +26,6 @@ if defined LS_JAVA_HOME (
   if exist "%LS_HOME%\jdk" (
     echo WARNING: Using LS_JAVA_HOME while Logstash distribution comes with a bundled JDK.
   )
-) else if defined JAVA_HOME (
-  set JAVA="%JAVA_HOME%\bin\java.exe"
-  echo Using JAVA_HOME defined java: %JAVA_HOME%
-  if exist "%LS_HOME%\jdk" (
-    echo WARNING: Using JAVA_HOME while Logstash distribution comes with a bundled JDK.
-  )
-  echo DEPRECATION: The use of JAVA_HOME is now deprecated and will be removed starting from 8.0. Please configure LS_JAVA_HOME instead.
 ) else (
   if exist "%LS_HOME%\jdk" (
     set JAVA="%LS_HOME%\jdk\bin\java.exe"

docs/static/jvm.asciidoc

@@ -47,14 +47,11 @@ Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.1+13-LTS, mixed mode)
 
 [float]
 [[java-home]]
-==== `LS_JAVA_HOME` and `JAVA_HOME`
+==== `LS_JAVA_HOME`
 
 {ls} uses the Java version set in `LS_JAVA_HOME`. The `LS_JAVA_HOME` environment
 variable must be set for {ls} to operate correctly.
 
-If {ls} doesn't find `LS_JAVA_HOME` it tries to fall back to `JAVA_HOME`.
-The usage of `JAVA_HOME` is now considered deprecated in favor of `LS_JAVA_HOME`.
-
 On some Linux systems, you may need to have the `LS_JAVA_HOME` environment
 exported before installing {ls}, particularly if you installed Java from
 a tarball. 

qa/acceptance/spec/shared_examples/installed_with_jdk.rb

@@ -24,7 +24,6 @@
   before(:all) do
     #unset to force it using bundled JDK to run LS
     logstash.run_command("unset LS_JAVA_HOME")
-    logstash.run_command("unset JAVA_HOME")
   end
 
   before(:each) do

qa/docker/shared_examples/container.rb

@@ -14,7 +14,7 @@
       console_out = exec_in_container(@container, 'logstash --version')
       console_filtered = console_out.split("\n")
             .delete_if do |line|
-              line =~ /Using LS_JAVA_HOME defined java|Using JAVA_HOME defined java|Using system java: /
+              line =~ /Using LS_JAVA_HOME defined java|Using system java: /
             end.join
       expect(console_filtered).to match /#{version}/
     end

qa/integration/specs/cli/prepare_offline_pack_spec.rb

@@ -86,7 +86,7 @@
       filters = @logstash_plugin.list(plugins_to_pack.first)
                                 .stderr_and_stdout.split("\n")
                                 .delete_if do |line|
-                                  line =~ /cext|├──|└──|logstash-integration|JAVA_OPT|fatal|^WARNING|^warning: ignoring JAVA_TOOL_OPTIONS|^OpenJDK 64-Bit Server VM warning|Option \w+ was deprecated|Using LS_JAVA_HOME defined java|Using JAVA_HOME defined java|Using system java: |\[\[: not found/
+                                  line =~ /cext|├──|└──|logstash-integration|JAVA_OPT|fatal|^WARNING|^warning: ignoring JAVA_TOOL_OPTIONS|^OpenJDK 64-Bit Server VM warning|Option \w+ was deprecated|Using LS_JAVA_HOME defined java|Using system java: |\[\[: not found/
                                 end
 
       expect(unpacked.plugins.collect(&:name)).to include(*filters)