Change getCallForwardingOption to specify voice service class.

When querying the CF status via the CommandsInterface, now specifying
the voice service class.

Test: Manually tested that this change does not cause regression.
Test: Added new unit test code.
Fixes: 71696037
Merged-In: I4ec38581882e24863f955b5a08118a2c4ed8dcf7
Change-Id: I4ec38581882e24863f955b5a08118a2c4ed8dcf7
(cherry picked from commit ec5c6e24)