Explain in error message how to recover from lock failure

Bug: 483897
Change-Id: I70f8d9c82c1efe2928f072a2fb69461160f7c5f7
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -77,7 +77,7 @@ cannotGetObjectsPath=Cannot get {0}/{1}: {2}
 cannotListObjectsPath=Cannot ls {0}/{1}: {2}
 cannotListPackPath=Cannot ls {0}/pack: {1}
 cannotListRefs=cannot list refs
-cannotLock=Cannot lock {0}
+cannotLock=Cannot lock {0}. Ensure that no other process has an open file handle on the lock file {0}.lock, then you may delete the lock file and retry.
 cannotLockPackIn=Cannot lock pack in {0}
 cannotMatchOnEmptyString=Cannot match on empty string.
 cannotMkdirObjectPath=Cannot mkdir {0}/{1}: {2}