RFR: 1229: Skara Backports handling needs to handle non backport type as backport

[Erik Joelsson]

This patch changes the Backports::findBackports method to no longer filter out issues that aren't of type "Backport" and just honor the "backported by" links as they are.

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Commit messages:
 - SKARA-1229

Changes: https://git.openjdk.java.net/skara/pull/1237/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1237&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1229
  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/skara/pull/1237.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1237/head:pull/1237

PR: https://git.openjdk.java.net/skara/pull/1237