Require OsmoMgw in OsmoBsc and update tests

Since Change-Id Ia2882b7ca31a3219c676986e85045fa08a425d7a, osmo-bsc
uses osmo-mgw and utilizes libosmo-mgcp-client to talk to it.

This commit fixes latest constant failures in voice suite.

Change-Id: I1dadd781a357fce33e7bde55e4bcbdaeb4633359
19 files changed