RFR: SKARA-1340: Correct email domain not always used when adding a contributor to a PR

[Guoxiong Li]

Hi all,

The contributor command uses the static domain `openjdk.org` which causes this issue. This patch uses the domain of the configuration instead of the static `openjdk.org`, changes the default domain to `openjdk.org` and adjusts the test cases.

Thanks for taking the time to review.

Best Regards,
-- Guoxiong

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Commit messages:
 - Change default domain.
 - SKARA-1340: Correct email domain not always used when adding a contributor to a PR

Changes: https://git.openjdk.java.net/skara/pull/1281/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=1281&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-1340
  Stats: 8 lines in 3 files changed: 1 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/skara/pull/1281.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/1281/head:pull/1281

PR: https://git.openjdk.java.net/skara/pull/1281