Telephony: Query SignalStrength when there is a RAT change.

In CdmaLte phone when RAT switch happens, telephony receiving
new signal info before updating to new RAT and because of that
the received signal info is ignored and empty bars updated
on UI. To avoid that query signal strength info when there
is a change in PS RAT happens.
CRs-Fixed: 464438

Change-Id: If494b9380f47bd82fe4f5dec03f9538c7ab76b49
Merge branch 'cm-10.2' of github.com:CyanogenMod/android_frameworks_opt_telephony into HEAD