Upgrade JGit to 60b81c5a9280e44fa48d533a61f915382b2b9ce2
Upgrade JGit to 60b81c5a9280e44fa48d533a61f915382b2b9ce2

This upgrade provides:
60b81c5a9 Fix RevWalk.getMergedInto() ignores annotated tags
c5b305473 Optimize RevWalk.getMergedInto()
847077151 GitServlet: allow to override default error handlers
35eeab41b RevWalk: getMergedInto's result is wrong on the second call
6cb39d145 [test] Create keystore with the keytool of the running JDK
ae081b8dc ReachabilityCheckerTestCase: fix reachable from self test case

Change-Id: Ibca76087d63149b8af9aa1d7d66f2e05a3486ac0

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