mbclient.c: contact() can return more than just -1 on failure
mbclient.c: contact() can return more than just -1 on failure

Fix one class of failure to re-register a client.

EV 380672  900FE w/ 4GB DIMM

Review-link: https://reviews.lpdev.prtdev.lexmark.com/r/44558/
Signed-off-by: Scott Arrington <4e51604abec5b02f40da0104ca5f857ad6059560@lexmark.com>

srwalter/membroker,srwalter/membroker