protocol: prohibit wildcarded requests for MDCX and DLCX

When a wildcarded request is made with a DLCX or MDCX command
the MGW will search for a free endpoint and continues the command
execution with that endpoint.

- Catch the wildcarded request early on DLCX and MDCX and return
  with an error code.

See also TTCN3 testcases:
MGCP_Test.TC_mdcx_wildcarded
MGCP_Test.TC_dlcx_wildcarded

Change-Id: Ia77d44a6a86083e62338e5845b553e5cf13ebd10
1 file changed