[JENKINS-15587] Diagnostics.
(cherry picked from commit eff5635b75a63a536f8ad24231b3eba3cbc4b63e)
[FIXED JENKINS-15587] Do not issue a warning about unparsable build timestamps if it is just a number, i.e. failed symlink.
(cherry picked from commit 06b92a49bf80debd4d9f2d334049d790d46c6081)
[FIXED JENKINS-18895] MavenModuleSetBuild.getResult is expensive.
(cherry picked from commit d1d524863cbb2f1f443fc4bf7c25933b7a31b85d)

Conflicts:
	changelog.html
[JENKINS-18895] Refined fix to not cache status during the build.
(cherry picked from commit 8d46aa6d976f5b0d89a4ad4969d455cd3a4add5c)
[FIXED JENKINS-18895] Refined fix once again.

(cherry picked from commit ec9b4f11866e80ae4a432b9127e71afddf30de86)