System Regions on the Master is broken

The parent issue broke our being able to host system regions only on the Master.

This broke a few tests that depend on this ability. Two of the below actually enable system regions on the Master for the test run. The remainder is the test that make sure this works.

TestMultiParallel
TestRegionsOnMasterOptions
TestRegionServerReadRequestMetrics

Parent changed the startup order. System regions and Master-as-a-RegionServer are having issues because we wait for regionservers to check in before completing Master startup which gets interesting when Master is supposed to act like a RegionServer. Previously, Master startup was off in a background thread.

Needs more thought but not required for beta-1.