Bug 861725 (follow-up) - Correct the logic of checking call forwarding reason. r=vicamo

We don't support A_CALL_FORWARDING_REASON_ALL and A_CALL_FORWARDING_REASON_ALL_CONDITIONAL
for now, because there is no detailed information about how to handle these two types in TS 22.082.
Merge pull request #99 from EdgarChen/bug_861725_followup

Bug 861725 (follow-up) - Correct the logic of checking call forwarding reason. r=vicamo