Block normal outgoing call when there's an ongoing emergency call.

Block non-emergency call if there's an ongoing emergency call when we
try to make room for outgoing calls. This can make sure that all
non-emergency call will be blocked even if the
NewOutgoingCallIntentBroadcaster wouldn't start the call immediately.

Bug: 186868542
Test: TelecomUnitTest
Change-Id: I9d21e8f23db6b725e978904919198ff9521dd633