4868 ifconfig(1M)'s "addif" uses an uninitialized mask if not specified
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Andy Stormont <AStormont@racktopsystems.com>
Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Approved by: Garrett D'Amore <garrett@damore.org>
	[illumos-gate merge]

commit 60b43c45a204a6c0651e8017e1e505015ba74094
    4868 ifconfig(1M)'s "addif" uses an uninitialized mask if not specified