Make the MGW pool configurable in the VTY and connect to each configured
MGW instance on start up. This is in preparation for the
subscr_conn_fsm, which will allocate own MGCP connections while
processing BSSMAP assignment request and related messages.
Related: SYS#5560
Change-Id: I6030a1f5a9d5fb06f148b2a2e03ae57bcb6b3766