Fix a few known issues in SensorService

This CL fixes a few known issues in sensorservice which is related
to newly added dynamic sensor discovery API.

  * check and ensure handle uniqueness for dynamically discovered
    sensor.
  * add mutex for synchronizing r/w of various sensor lists.
  * ensure dynamic sensor list is reported sorted by handle.
  * code format fix

Bug:
b/27911774

Change-Id: Iec6df90ae150321ea9e4309b2ac1200b8dc37f05