MGCP_Test: Add VTY access

The MGCP_Test testsuite currenty lacks VTY access capabilities, lets
add them so that future testcases can access the VTY in order to change
options on the fly.

Depends: osmo-ttcn3-hacks Ife949c61156222de3026280071226ef6f5dbd959
Change-Id: If383f81af3306f8f5bdf50152498ae1303d390df
Related: OS#3807
4 files changed