msc_mgcp: do not send wildcarded DLCX messages

If an error on the MGW side occurs, the MSC may send out
a DLCX command that contains a wildcarded endpoint name.
Wildcarded DLCX commands are legal in principle but not
in the context of an error on a single endpoint. Apart
from that osmo-mgw is (not yet) capable to handle
wildcarded DLCX command.

The problem is caused by a wrong error handling. When the
first (RAN) CRCX fails the error handling logic tries to
perform a DLCX, but since we did not receive a specific
endpoint name yet, the buffer containing the endpoint name
is still initalized with the wildcarded enpoint name, but
the error handler and the code that generates the DLCX is
not aware of that.

- Perform a check in the error handler function that
  checks if a DLCX can be made (a specific endpoint
  name is set

- Correct the flags in the code that handles the first
  CRCX so that no DLCX is requested in the case of error

Related OS#2882

Change-Id: I64c2a82016d854ad446fd49a5d76a28324e8bd4b
1 file changed