Do not disconnect voice calls during phone object switch.

In cases like emergency call attempted in oos or IMS SRVCC
there is possibility that the phone object switch due to
RAT change can happen while a voice call is in progress.
To avoid call disconnect in such cases, do not hangup connections
while disposing CallTracker objects.

Change-Id: I890d6bcea958288eab8f557073f871820ddd3b52

Conflicts:
	src/java/com/android/internal/telephony/cdma/CdmaCallTracker.java
	src/java/com/android/internal/telephony/gsm/GsmCallTracker.java