interval change should restart thread reporting locations

Also updates the mockLocation's bearing and speed to be non-zero, since
a real location rarely has exactly 0 bearing or 0 speed.

Bug: 384699906
Test: atest android.location.cts.gnss.GnssLocationUpdateIntervalTest#testLocationUpdatesAtVariousIntervals
Change-Id: I67d513eea50d1399b52aef3e07a73ff31db24ace