Some interactions between camera service and hwservicemanager require
multiple threads to execute without deadlocks, such as calling
getService() from within an onRegistered() callback.
Increase thread count to 3 to accomodate.
Also switch the order of listener registration and legacy provider
addition back to what it was originally.
Test: No deadlock when camera service is restarted
Bug: 35096594
Change-Id: I6def961d5765958fef284c0a1820e903abc851ef
Eino-Ville Talvala
Chien-Yu Chen