Fix for PR 82974.  We were not checking that the route looked up in the case of an RTM_CHANGE was specific, i.e. that it matched completely.  This led to a route change of a non-existent route changing the default route as the radix code would simply back track to that point and hand that route back to the routing socket code.
Fix for PR 82974.  We were not checking that the route looked up in
the case of an RTM_CHANGE was specific, i.e. that it matched completely.  This
led to a route change of a non-existent route changing the default route
as the radix code would simply back track to that point and hand that
route back to the routing socket code.

PR: 82974
Reviewed by: Tai-hwa Liang <avatar@mmlab.cse.yzu.edu.tw>
             Ben Kaduk <minimarmot@gmail.com>
             Bjoern A. Zeeb <bzeeb-lists@lists.zabbadoz.net>
Obtained from:	OpenBSD with modifications.
MFC after: 2 weeks

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