mgcp: add prefix to virtual trunk

the virtual trunk is addressed without a prefix (just *@domain).

- reorganize find_endpoint() so that it accepts a prefix when
  addressing the virtual trunk.

- do no longer accept wildcarded CRCX requests without prefix
  (will not break anything, the feature of wildcarded CRCX is
  not in use yet)

- keep the old prefix-less method but print a warning that it is
  depreacted.

Change-Id: I2aac3ba0f1f3122dfbb3bf36f74198ecb2b21de5
3 files changed