RFR: 1329: incorrect hgupdate label for JDK 7 updates

[Erik Joelsson]

This patch adds special handling of Backports for a couple of historic releases where we have 30 or more builds (and no BPRs).

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Commit messages:
 - SKARA-1329

Changes: https://git.openjdk.java.net/skara/pull/1280/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1280&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1329
  Stats: 64 lines in 2 files changed: 54 ins; 2 del; 8 mod
  Patch: https://git.openjdk.java.net/skara/pull/1280.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1280/head:pull/1280

PR: https://git.openjdk.java.net/skara/pull/1280