Telephony: Handle race condition during sim deactivation.

Issue:
- config L/W/G + 1x
- DDS sim is deactivated. DDS is being auto switched to 1x sub.
- Modem/qcril reports 1x subscription in service before QtiDctController
  gets a chance to processRequests or could request EVENT_CONNECT to
  DcSwitchStateMachine.
- During this window both of the DcSwitchStateMachines are IDLE.
- ATTACHED event is handled by 1x DcSwitchStateMachine and it moves from
  IDLE to ATTACHED state without sending ALLOW_DATA(T) to modem.

Solution:
- Since the race conditon is due to the fact the both
  DcSwitchStateMachine are IDLE and ATTACHED event is handled before
  EVENT_CONNECT. The solution is to defer the ATTACHED event
  IFF DcSwitchStateMachine is IDLE and belongs to DDS sub also
  transition to ATTACHING state.
- As we enter into ATTACHING state we would send out ALLOW_DATA(T)
  and the deferred event ATTACHED would be handled in this state
  which would kick us to ATTACHED state.This way modem and telephony
  both would be in sync with respect to DDS movement for this usecase.

Change-Id: I8c7e0ea4d8a7c919703ef22c5df1b94902ab830c