MFC r225849:

MFC r225849:

Test if the interface is afif in dhcpif() and syncdhcpif(), as
done in ipv6_autoconfif.

This fixes a regression that causes e.g. ifconfig_DEFAULT="DHCP"
to run on non-afif interfaces like pfsync0, which in turn would
cause excessive delay on system startup.

Sponsored by:	iXsystems, Inc.
Reviewed by:	hrs (freebsd-rc@)
Approved by:	re (bz)

git-svn-id: svn://svn.freebsd.org/base/releng/9.0@227910 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f