telephony: Support broken RIL implementations without CALL_RING events

This is probably specific to the LGE star: Extend the call_ring.multiple
configuration to the ringing connection event, since the CALL_RING event
itself doesn't appear. Without this, only the first ring happens.

Enable with ro.telephony.call_ring.absent=true

Change-Id: Idd272583769757c6baa638fd644b5b919cf80fec