RFR: 1030: Lots of "uncleanable" repos found in scratch dirs

[Erik Joelsson]

This patch tries to fix a problem where bots will often generate "uncleanable" repos in the scratch area. This is often caused by the initial clone of the repo being interrupted for some reason (usually bot restart). By cloning into a temp dir and then moving in place, we can easily tell if an existing scratch repo was fully cloned or not.

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Commit messages:
 - Add logging
 - SKARA-1030

Changes: https://git.openjdk.java.net/skara/pull/1156/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1156&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1030
  Stats: 10 lines in 1 file changed: 9 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/skara/pull/1156.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1156/head:pull/1156

PR: https://git.openjdk.java.net/skara/pull/1156