[FIXED JENKINS-27256] Added functional test for stapler fix

* master:
  Updated changelog
  updated changelog as a part of the release
  [maven-release-plugin] prepare for next development iteration
  [maven-release-plugin] prepare release jenkins-1.604
  Noting #1597
  Noting #1593, #1579, move JENKINS-22346, #1558
  Remove two fixes that were backported to RC
  JENKINS-27183 Avoid deadlock when using build-monitor-plugin

[FIXED JENKINS-27183] Avoid deadlock when using build-monitor-plugin

[FIXED JENKINS-27256] Added functional test for stapler fix to handle dispatcher methods for getX(long) model methods

The original motivation for the fix (to prevent users from logging in
once he's removed from the backend identity database) is legitimate,
but it affected too many users.

So as an escape hatch / non-promoted feature switch, I'm adding this
option to bring back the old behaviour.

[JENKINS-26723] Expose displayName in Remote API

Spotted a HUDSON variable in debian default file

show « check now » button on PluginManager updates and available pages

(cherry picked from commit cf2b02dc)

Conflicts:
	changelog.html

(cherry picked from commit 87ab95e7)