mgcp_test: do not access endpoint array elements directly

The test assumes that the endpoint "rtpbridge/X@mgw" is at array
position X in many places. This does not necessarly have to match.
Accessing the array elements directly was the prefered way when the MGW
did use integer numbers and not strings to identify endpoints. Since the
endpoint name strings are used to access the endpoints the unit-test
should also reflect this.

Lets replace the integer variable last_endpoint with a string variable
and do related verifications based on strings.

Change-Id: Ic950c427f23be4a792af94972554637c2b0fbdf2
Related: OS#2659
1 file changed