Stop current tuning before starting a new tuning.

If a new tuning request comes before stop old tuning, there is race
condition that the Frontend loop thread may crash while terminate().

Bug: 202335601
Fix: 202335601
Test: atest android.media.tv.tuner.cts
Change-Id: Ic168b585f0a8fe36bd8eeceee3e0b4c83d5388aa
1 file changed