Need to call resetFgsRestrictionLocked() before calling

setFgsRestrictionLocked() again.

Bug: 191159915
Test: atest cts/tests/app/src/android/app/cts/ActivityManagerFgsBgStartTest.java#testStartForegroundTimeout
Change-Id: Iedd6f4507fc3ac136a0f62385c0f8b49d43ff778