Fix data disconnect issue on G sub for C+G DSDS

On a DSDS Cdma+Gsm device, when data is registered on both Cdma and Gsm
subscriptions and DDS is on Gsm sub, if data deregister happens on Cdma
sub, data disconnect is getting propagated to connectivity service
irrespective of DDS, hence data is getting disconnected on Gsm sub.

Add code changes to block data disconnect getting propagated to
connectivity service when the subscription is not DDS.

Change-Id: I329d6a20ace65cad494e36dd9ec5a6470db2fbd7
CRs-Fixed: 544292