Fix dialer cts test

Whether setting default dialer succeeds is propagated all the way to API,
and (apparently) enforced by cts, so it looks like we should wait for it

Fixes: 123718729
Test: atest android.telecom.cts.DefaultDialerOperationsTest#testSetDefaultDialerNoDialIntent_notSupported
Change-Id: I2f7b8d4a32d1b570d0aba8cc4cc529f58a9dbc20