RFR: 934: Bots incorrectly assigned "build" label despite no obvious matching rule

[Robin Westberg]

When determining the set of file names to evaluate for determining label assignment, only include the source name for deletions and renames (and not for copies, for example).

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Commit messages:
 - Only match the source name for deletions and renames

Changes: https://git.openjdk.java.net/skara/pull/1118/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1118&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-934
  Stats: 57 lines in 2 files changed: 55 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/skara/pull/1118.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1118/head:pull/1118

PR: https://git.openjdk.java.net/skara/pull/1118