mbclient.c: clear address family in free so that next open will connect
mbclient.c: clear address family in free so that next open will connect

Fix another class of problem with a client attempting to unregister
and re-register.

EV 380672  900FE w/ 4GB DIMM

Review-link: https://reviews.lpdev.prtdev.lexmark.com/r/44559/
Signed-off-by: Scott Arrington <4e51604abec5b02f40da0104ca5f857ad6059560@lexmark.com>

srwalter/membroker,srwalter/membroker