Bolster outgoing call_screen.py wait

Enhance this wait as this number being set set via javascript is one of the last things to be done.
This was causing a sporadic failure of test_call_contact.py.

NB this works whether the value in the outgoing call screen is a string or a phone number.

NB part 2, this test is still XFailed but I was investigating it and decided to make this patch.

`v1.0.1?` low risk, could be merged in.