[FIXED JENKINS-9679] integrated remoting 2.21 that contains the fix.
(cherry picked from commit 8a4bedd0df9b5d642945eb601ddb99bb75e87131)

Conflicts:
	changelog.html
	pom.xml
[JENKINS-16342] Improving responsiveness of asynchPeople when Gravatar plugin is in use.
This change does not necessarily improve total performance, since the avatar is still computed.
But (1) the computation is correctly done in the work thread, not in the HTTP response thread;
(2) the computation is done just once for a given User, which could reduce load when many AJAX checks are done.(cherry picked from commit c757e65431ad1aec9a3bebe81ac919577e51ac58)

Conflicts:
	changelog.html