adding yum repo flag for Redhat

In environments where RHEL uses Satellite or production servers can't
reach out to the internet, and the Yum repo is not wanted. This commit
adds a flag to disable the functionality. It also removes the
enablerepo: nginx line from the package since a) it's redundant and b)
working around it overly complicates  the situation.

defaults/main.yml

@@ -2,6 +2,9 @@
 # Used only for Debian/Ubuntu installation, as the -t option for apt.
 nginx_default_release: ""
 
+# Used only for Redhat installation, enables source Nginx repo.
+nginx_yum_repo_enabled: true
+
 # Use the official Nginx PPA for Ubuntu, and the version to use if so.
 nginx_ppa_use: false
 nginx_ppa_version: stable

tasks/setup-RedHat.yml

@@ -6,9 +6,9 @@
     owner: root
     group: root
     mode: 0644
+  when: nginx_yum_repo_enabled
 
 - name: Ensure nginx is installed.
   yum:
     name: "{{ nginx_package_name }}"
     state: installed
-    enablerepo: nginx