[SPARK-9649] Fix flaky test MasterSuite again - disable REST

The REST server is not actually used in most tests and so we can disable it. It is a source of flakiness because it tries to bind to a specific port in vain. There was also some code that avoided the shuffle service in tests. This is actually not necessary because the shuffle service is already off by default.

Author: Andrew Or <andrew@databricks.com>

Closes #8084 from andrewor14/fix-master-suite-again.