[Integrated] RFR: Cache labels in GitHubPullRequest

[Erik Helin]

Changeset: c586baf9
Author:    Erik Helin <ehelin at openjdk.org>
Date:      2019-12-05 09:50:32 +0000
URL:       https://git.openjdk.java.net/skara/commit/c586baf9

Cache labels in GitHubPullRequest

Reviewed-by: rwestberg

! forge/src/main/java/org/openjdk/skara/forge/github/GitHubPullRequest.java