libosmo-mgcp-client is GPLv2+, not AGPLv3+

The client library should be usable to all GPLv2/v3/AGPLv2/v3 programs,
so like our general project practises, let's put it under
GPLv2-or-later.  I believe this was unintentional from the beginning.

Our general policy has been:
* libraries under GPLv2-or-later
* applications under AGPLv3-or-later

Change-Id: I29ed7edc510dba67d28b9247aecb4d6d5d25cc0c
3 files changed