Stop duplicate RADIO_POWER indcation when power off delay disabled

When the power off delay for IMS registration feature is disabled,
do not allow registration changes trigger EVENT_CHANGE_IMS_STATE or
in some cases it will trigger a duplicate RADIO_POWER event to the
modem before the previous event completed.

Fixes: 189524310
Test: atest FrameworksTelephonyTests:ServiceStateTrackerTest
Merged-In: I37189e2d724809425092d1a5cc0943c774a7dc22
Change-Id: I37189e2d724809425092d1a5cc0943c774a7dc22