Fix potential test issue related to metrics in ImsPhoneConnection.

Allow for mocking of the TelephonyMetrics instance used in the test.
This is not related to what this particular test is testing.  Although
it runs fine locally it seems in cloud testing there are some dependencies
not being met.

Fixes: 186693611
Test: Modify unit test
Change-Id: Ie75419397c01cc0329201a55969432e56c048c8f