Disable Telephony service handle caching while testing.

Some telephony tests utilize mock instances of services to test
client-side code. Efforts to cache service handles in ag/9592007
interfered with this, so we now disable service handle caching during
Telephony tests.

Test: atest PhoneSubInfoControllerTest and atest DcTrackerTest
Bug: 140788621
Change-Id: Ie33af533eeeac63fd37071294aa9512cca41a206