Prevent unwanted retry for PS attach failure.

Issue: Two back to back DDS switch requests were received.
Allow data request for the first switch failed from RIL and the
the second DDS switch request succeeded. Due to retry for the first
failed request, DDS was switched back to previous DDS sub.

Fix: Assign a unique tag value for each PS attach/DDS switch request.
When response for a failed allow_data request is received, attempt
retry only if it has the current tag.

Change-Id: Ia96768a827c565c98d6f3110d7c60a312134b67d
CRs-Fixed: 785709