Fix the misuse of calling user id as group id

1. The userId stored in different clients are actually calling user id.
groupId should be used to do all the operations. Also, renamed the variable
to avoid further confusion.

2. Fix the bug null is always returned in getFingerprintDaemon
   in RemovalClient.

3. Fix the misuse of calling uid as calling user id in startAuthentication.

Fix: 28268635
Fix: 28264725

Change-Id: I618ac3c6d913ae5c86e7b04cb3f9ead39828f216