Remove pending JGit locks if found and lock access to Git repo of Git Component Repo with safe file lock
See https://www.eclipse.org/forums/index.php?t=msg&th=1102984&goto=1823307&#msg_1823307 for more details.
Currently JGit may leave blocking file locks when crashing. As that may prevent z2 from starting up, and as z2 is the only process that legitimately access the GitCR Git repo, we can
lock externally using a safe java.nio.channels.FileLock based mechanism.
- Lock fetch on the git repo in the gitcr using LockingRevFile.
- If finding a .git/index.lock at fetch time, delete it.