Fix problems with two quick updates of the same PR

[marcusnaslund]

Still having problems, like:

Added pull request: [IntVectorList contains() - https://github.com/cogneco/ooc-kean/pull/1092]
Updated pull request: [IntVectorList contains() - https://github.com/cogneco/ooc-kean/pull/1092]
Aborting job queue for: ooc-kean 1092
The following 1 job queues are running
-> ooc-kean 1092
Failed when processing pullrequest for 1092 IntVectorList contains() with the error: Error: ENOENT, no such file or directory '/home/mnaslund/repositories/ooc-kean/1092/ooc-kean/.git/config'
ooc-kean 1092 finished job: Git clone with status: SIGTERM
The following 0 job queues are running

[marcusnaslund]

Currently fixed as it won't occur with labels, but could still happen with two quick pushes.