MGCP_Test: add E1 related testscases

osmo-mgw recently added support for E1 trunks via libosmoabis. While the
actual E1 plane may be difficult to test, there is some functionality
that can already be tested without having E1 support in TTCN3.

Lets add three testcases:
- TC_e1_crcx_and_dlcx_ep:
  Does a CRCX to an E1 endpoint followed by a DLCX
- TC_e1_crcx_with_overlap:
  Not all E1 endpoint combinations are possible at the same time. This
  test verifies that invalid endpoint combinations are prevented.
- TC_e1_crcx_loopback:
  Opes an E1 endpoint and tests if RTP loopback works (NO E1 traffic
  involved)

Change-Id: I673eeffcb3012b42f039789960c54d99282e1aad
Related: OS#2659
1 file changed