Changes

mgcp_test.c: fix various missing '\r' and '\n'

The only valid line endings are '\n' and '\r\n'.
We usually use '\r\n' like we were in MSDOS.

MGCP, RFC3435 3.1:

   Headers and session descriptions are encoded as a set of text lines,
   separated by a carriage return and line feed character (or,
   optionally, a single line-feed character).

SDP, RFC8866 5:

   The sequence CRLF (0x0d0a) is used to end a line,
   although parsers SHOULD be tolerant and also accept lines terminated
   with a single newline character.

There should probably be tests for '\n' line endings, but mixing them in
the same MGCP message is ridiculous.

Change-Id: I6d530535a3a5f1d1a0716ab9e4a8079ba1de242e