MINOR: Enable "abort previous builds" for PRs (#12588)
MINOR: Enable "abort previous builds" for PRs (#12588)

When a new commit is pushed to a PR, we should abort the build
and start a new one instead of queuing one build per commit.
This reduces wasted resources and provides the desired feedback
faster (since we only care about the build results for the last
commit in the PR).

Reviewers: Luke Chen <a747209bc9e65a9d7dd7589245c91b7bed721b13@gmail.com>
guozhangwang/kafka,guozhangwang/kafka,guozhangwang/kafka,apache/kafka,apache/kafka,guozhangwang/kafka,apache/kafka,apache/kafka