Fix DDS switch issue from GSM to CDMA.

CDMA data remains in attached state irrespective of ALLOW_DATA
true/false requests. Hence when switching DDS from G to C, there
won't be any attached event on C subscription and
DcSwitchStateMachine remains in Attaching state.
To fix this, directly move from Attaching to Attached state if
data is already registered.

Change DDS switch implementation to set the new DDS setting
only after DctController completes switch operation.

Remove extra setDataAllowed call from DcSwitchStateMachine
Attaching state.

Change-Id: I4ee3ca59e874c6ac2de8d46d3e5f9358d9cf0b0d
CRs-Fixed: 812478