Avoid ANR due to no response to getForbiddenPlmns()

Pending response message for getForbiddenPlmns() can be left in HashMap
when no data or exception is returned by the lower layer. Response shall
always be made regardless of the result of the RIL command in order to
avoid ANR issue in the application layer.

Bug: 143184103
Test: Confirmed the expected response in manual test.

Change-Id: I282378930a0cc6e0e30c11621b3513edab7bab81