Delete sample changelog at end of test - check for open file leak

JENKINS-20585 reports that changelog.xml cannot be deleted on Windows
because it is held busy by a process.  This test assumes that process
is Jenkins itself, and that the GitChangeLogParser.parse() method is
the most likely culprit.
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Update git-client dependency now that 1.6.0 has been released
Merge pull request #184 from MarkEWaite/master-pom-update-jgit-client-1.6.1-SNAPSHOT

Update jgit-client version in pom to git-client 1.6.1-SNAPSHOT