[SPARK-3101] Missing volatile annotation in ApplicationMaster

[sarutak]

No description provided.

[SparkQA]

QA tests have started for PR 2016 at commit 7b89201.

• This patch merges cleanly.

[SparkQA]

QA tests have finished for PR 2016 at commit 7b89201.

• This patch passes unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

QA tests have started for PR 2016 at commit 92c25ca.

• This patch merges cleanly.

[sarutak]

#2022 changed ApplicationMaster and ExecutorLauncher so rebased this PR.

[SparkQA]

QA tests have finished for PR 2016 at commit 92c25ca.

• This patch passes unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[JoshRosen]

@vanzin @tgravescs If this is a good fix, you may want to incorporate it into #2020 yourselves (I don't want to create even more merge conflicts for you).

[vanzin]

@JoshRosen already added to my code, will update PR shortly. Thanks for pointing it out.

[JoshRosen]

@sarutak I think this has been subsumed by #2020, which was merged yesterday, so do you mind closing this pull request if all of your changes have been incorporated? Thanks!

[sarutak]

@JoshRosen O.K, I close this PR.