update release notes for change in agent timeouts and message auth.
PR review comments.
Merge branch 'master' into jortel-2.4-releasenotes

Conflicts:
	docs/sphinx/user-guide/release-notes/2.4.x.rst
Merge pull request #851 from pulp/jortel-2.4-releasenotes

update release notes for change in agent timeouts and message auth.