Data recovery failure due to apn/dc state stuck in "disconnecting"

If rild is reset while RIL_DEACTIVATE_DATA_CALL is pending
response, the ApnContext is not force cleaned up since
link to DCAC is cleared in the begining of release.

This patch fixes:
1) Hold DCAC reference until the DC is disconnected. This is
   to ensure DC won't be stuck in DcDisconnectingState so force
   reset can kick in.
2) In "clearCleanUpConnection", make sure the status of ApnContext
   can be reset to IDLE even if no reference to DCAC.

Change-Id: Ic69271da7c6bc9dcb2c38ec53a9bd2e8ce785adc