Always quit state machines once removing them

When removing state machines from our maps and dropping their
references, there's a chance we leak their underlying threads if the
state machines are not quit.

This change adds doQuit() or quitNow() calls in places where we remove
state machines and drop their references.

Tag: #stability
Bug: 293920022
Test: atest BluetoothInstrumentationTests
Change-Id: I1ff69590a204eb7e92619d0ed6584ba2c27b1b3d