add CTS coverage for SM calls with sim based defaults

While creating some CTS tests that changed the default
phone account handle, I noticed the handle was not changing.
After looking through the logs, I discovered that since test handles
are given a subid=-1, SubscriptionMananger#setDefaultVoiceSubId would
then re-call setUserSelectedOutgoingPhoneAccount again and override
the new default phone account with null.

Therefore, to prevent this override on test handles, a new early exit
was put in.

bug: 234846282
Test: android.telecom.cts.SelfManagedConnectionServiceTest
    #testSelfManagedCallWithSimBasedPhoneAccountAsDefault
    #testSelfManagedCallWithNoCallPreferenceAsDefault
    #testSelfManagedCallWithMultipleSimBasedAccountsActiveAndAsDefault
Change-Id: If5d15b32e8fcdab758a44e31edd9af85cc02242f