Eliminate unused parameter to initializeServerGlobalState().
Fork earlier in server startup; will simplify logging initialization.

Ensures that server initialization happens in the process that will actually
host the server, rather than the process that forks the server.

Also, when startup fails in mongos, exit with a failing code.
Revert "Fix parallel tests by dropping all databases before starting"

This reverts commit babd275f88181c3f2cd29585816aab24bc4b421c.
Fix some tests to work in parallel suite by dropping system.users at the beginning of the test