Fail handover request if source data connection not in correct state

We should fail the handover request if the source data connection
is not in the right state. This can prevent sending unnecessary
handvoer requests to the modem.

Bug: 139702206
Test: Telephony sanity tests
Merged-In: Id28d6a57583c9ccb5cdc381ab7a2bfdc31752035
Change-Id: Id28d6a57583c9ccb5cdc381ab7a2bfdc31752035
(cherry picked from commit 782f5cde)