Skip unbinding from default dialer if we tried to switch to a

unavailable InCallService.

When automotive projection set but the car mode InCallService is
disabled, Telecom used to first unbind from default dialer and then
tried to bind to the disabled car mode app. Skip this step if we find
that the InCallService is not available.

Bug: 218357441
Test: CarModeInCallServiceTest
Change-Id: I8f81bb8a2184dcbdde6599286eaf37099c10a995