[SPARK-13344] [TEST] Fix harmless accumulator not found exceptions

[andrewor14]

See JIRA for more detail. This was caused by #10835.

[SparkQA]

Test build #51376 has finished for PR 11222 at commit c1df4ff.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • class SaveLoadSuite extends DataSourceTest with SharedSQLContext with BeforeAndAfterEach

[JoshRosen]

As it turns out, there's still tons of other suites which hit this same problem. I think we should pursue a more general fix which addresses all of the other cases, too.

[andrewor14]

Alright, the latest commit should fix it for all the tests

[JoshRosen]

LGTM pending Jenkins.

[SparkQA]

Test build #51442 has finished for PR 11222 at commit c0a2933.

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