templates: osmo-bsc.cfg.tmpl: migrate to separate 'mgw' node
This commit fixes the following deprecation warnings:
% MGCP commands outside of 'mgw' nodes are deprecated.
You should consider reading the User Manual and migrating to 'mgw' node.
Change-Id:
Ic2b3c8a6775b6a34bfc03e0643a34772ae789139