Telephony: Handle PS Detach failure

In DSDS, PS DETACH on DDS sub can fail if there is MT page/connection
or MO SMS in progress at the same time. As a result, data connection
on DDS sub will not be torn down. DdsScheduler will be stuck in DdsSwitch
state unable to process further DDS switch requests.
Handle this by notifying DdsScheduler of the failure so that it goes back to
IdleState to process further requests.

CRs-Fixed: 759265

Change-Id: Id33d2dbff3be6edd9f865b78b3ba06ba840edf10