MGCP_Test: Clean up after TC_crcx_sdp

The testcase TC_crcx_sdp does not clean up the connection it
created. This can cause subsequent tests to fail.

- Use f_dlcx_ok() to clean up the connection once the test
  is done.

Change-Id: I4e0f5ce218fadc5debe0bbf548b69919584ab66c
1 file changed