Avoid deadlock if HAL dies at init

The SensorDevice constructor is invoked with the Singleton lock held, so
ensure we won't attempt to call getInstance() from this context via
handleHidlDeath().

Bug: 133445520
Test: use custom HAL that crashes at first getSensorList query, verify
      framework does not deadlock
Change-Id: Ia0903412cdb30474c962687bc95b8df6bf2df25e