1103232 - Document common proxy config options.

https://bugzilla.redhat.com/show_bug.cgi?id=1103232
Merge branch '1103232' into 2.4-release

Conflicts:
	docs/sphinx/user-guide/server.rst
Merge branch '2.4-release' into 2.4-testing
Merge branch '2.4-testing' into 2.4-dev
Merge branch '2.4-dev' into 2.5-testing
Merge branch '2.5-testing' into 2.5-dev