Fix StateMachine init/quit race.

The quitNow method places the SM_QUIT_CMD at the front
of the queue. This can cause StateMachine to throw exception
if it has not yet processed the SM_INIT_CMD from start().

Bug: 67370902
Test: make checkbuild
Test: StatMachineTest unittest
Change-Id: I409242845854e70b77ad9b2378b69faed076847c
Merged-In: I7cec7bb91e0447e3c565d33cb7c34ccf59566639