Update core/src/test/java/hudson/model/RunTest.java

Added testParseTimestampFromBuildDir to deal with JENKINS-15587.
(cherry picked from commit 548503c45aab1c71ca40e7aec378831d62a60f43)

Conflicts:
	core/src/test/java/hudson/model/RunTest.java
Minor updates.

Code style convention related updates.

(cherry picked from commit 8f6a22297ea0ba12c9f8425248898b09caa2cca6)

Conflicts:
	core/src/main/java/hudson/model/Run.java
	core/src/test/java/hudson/model/RunTest.java
Massaging the fix.

- ID_FORMATTER is time zone sensitive, so comparing against # of
  milliseconds since the epoch won't be portable.

- resolveSymlink can return a relative path.

(cherry picked from commit 2f781863f5cf19358606989cb198d9223f7e763a)
[JENKINS-15587] Diagnostics.
[FIXED JENKINS-15587] Do not issue a warning about unparsable build timestamps if it is just a number, i.e. failed symlink.