Switch back to using rabbitmq-plugins from system path, drop Puppet 3…

… conditional (#566)

lib/puppet/provider/rabbitmq_plugin/rabbitmqplugins.rb

@@ -1,10 +1,16 @@
 require File.expand_path(File.join(File.dirname(__FILE__), '..', 'rabbitmqctl'))
+require 'mkmf'
+
 Puppet::Type.type(:rabbitmq_plugin).provide(:rabbitmqplugins, parent: Puppet::Provider::Rabbitmqctl) do
-  case Facter.value(:osfamily)
-  when 'RedHat'
-    has_command(:rabbitmqplugins, '/usr/lib/rabbitmq/bin/rabbitmq-plugins') { environment HOME: '/tmp' }
+  # Prefer rabbitmq-plugins if it's in $PATH, but fall back to /usr/lib/rabbitmq/bin
+  if find_executable 'rabbitmq-plugins'
+    has_command(:rabbitmqplugins, 'rabbitmq-plugins') do
+      environment HOME: '/tmp'
+    end
   else
-    has_command(:rabbitmqplugins, 'rabbitmq-plugins') { environment HOME: '/tmp' }
+    has_command(:rabbitmqplugins, '/usr/lib/rabbitmq/bin/rabbitmq-plugins') do
+      environment HOME: '/tmp'
+    end
   end
 
   defaultfor feature: :posix