r316487 altered the defined values of rc_force from "yes" (for yes)
and NULL (for no) to "no" (for no) and no change to the definition
of yes. Two rc.d scripts, dhclient and bgfsck check rc_force for
yesi, using test -n, and no, using test -z. The redefinition of
yes and no by r316487 caused rc.d/dhclient, when invoked by devd
using a devd.conf rule, to assign DHCP assigned IP addresses for
interfaces with statically assigned interfaces, breaking boot.
Point of breakage was at line 25 of etc/rc.d/dhclient (r301068)
where $rc_force needs to be NULL.

MFC after: 3 weeks
X-MFC with: r316487