[FIXED JENKINS-7806] changed wording of "slave back online" button

Changed from
  "This node is back online"
to
  "Bring this node back online"

Conflicts:

	changelog.html

(cherry picked from commit 2e5a7bf4)

Prevent NPE when a task is assigned to an executor which has disappeared
Thanks!

This reverts commit 9a1ad74b. The bits
aren't yet synchronized to central apparently.

Conflicts:

	changelog.html

This is also related to [JENKINS-9778].

[FIXED JENKINS-8214] Added a DISCOVER permission to allow anonymous users to be presented the login screen when accessing job URLs

[FIXED JENKINS-8214] Added a DISCOVER permission to allow anonymous users to be presented the login screen when accessing job URLs

[FIXED JENKINS-13564] If there is any problem when searching for user partipication in the build, end up more gracefully.

CauseOfBlockage not displayed when build blocked by QueueTaskDispatcher.canRun()

[JENKINS-10880] output the job when polling fails