[Midnightbsd-cvs] src: devfs_rule.c: Handle the special ruleset 0 in devfs_ruleset_use().

[laffer1 at midnightbsd.org]

Log Message:
-----------
Handle the special ruleset 0 in devfs_ruleset_use(). An attempt set the
current ruleset to 0 with command "devfs ruleset 0" triggered a KASSERT
in devfs_ruleset_create().

Modified Files:
--------------
    src/sys/fs/devfs:
        devfs_rule.c (r1.3 -> r1.4)
        (http://cvsweb.midnightbsd.org/src/sys/fs/devfs/devfs_rule.c?r1=1.3&r2=1.4)