Abort parsing in case of format error

Usecase:
1. Enable hf client and connect to AG.
2. Send +COPS with length more than allowed 16 characters.

Failure:
Crash might be seen while parsing +COPS response from AG.

Root cause:
sscanf used for parsing the AT commands does not update
the characters scanned when there is format error.

Fix:
Abort the processing in case of format error.

Change-Id: Id3ca80712df3d0251cf9ffb04d9c766be809ae84