Change test_dialer to wait for the call to be in dialing state

This test was sporadically failing for two reasons.. 
1. Changes to the timing and speed of the dialer making a call
2. The number we are calling sometimes letting it ring and sometimes picking up immediately.
I've gathered this information after speaking to ettienne.

I've changed the test to just wait for the call to be in 'dialing' state rather than the alerting state. alerting corresponds with an actual ring but that clashes with the two reasons above. This is also still compatible with testing outside of CI.

Ideally we need a remote number that lets the call dial a few times while we assert the call's state.