git: openjdk/skara: Avoid running PullRequestBot WorkItems for the same PR concurrently

[duke]

Changeset: 417c6f5f
Author:    Robin Westberg <rwestberg at openjdk.org>
Date:      2019-08-29 13:01:41 +0000
URL:       https://github.com/openjdk/skara/commit/417c6f5f

Avoid running PullRequestBot WorkItems for the same PR concurrently

Reviewed-by: ehelin

! bots/pr/src/main/java/org/openjdk/skara/bots/pr/CheckWorkItem.java
! bots/pr/src/main/java/org/openjdk/skara/bots/pr/CommandWorkItem.java
! bots/pr/src/main/java/org/openjdk/skara/bots/pr/LabelerWorkItem.java
+ bots/pr/src/main/java/org/openjdk/skara/bots/pr/PullRequestWorkItem.java