Skip system dialer FGS grant if no dialer role is present.

Ensure we don't try to do the grant if there is no dialer role on the
device.

Test: updated test assumptions to match grant behavior.
Flag: android.app.system_dialer_phone_call_fgs_grant
Bug: 435713951
Bug: 425971621
Change-Id: I40174ff112ea5373fddb6573ccbdd84ee76e500a