MFC 198301

MFC	198301

In the ARP callout timer expiration function, the current time_second
is compared against the entry expiration time value (that was set based
on time_second) to check if the current time is larger than the set
expiration time. Due to the +/- timer granularity value, the comparison
returns false, causing the alternative code to be executed. The
alternative code path freed the memory without removing that entry
from the table list, causing a use-after-free bug.

Reviewed by:	discussed with kmacy
Approved by:	re
Verified by:	rnoland, yongari

git-svn-id: svn://svn.freebsd.org/base/stable/8@198308 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f