when unmounting tmpfs file systems at shutdown time, avoid unmounting
a tmpfs created by init on /dev - behaviour overridable from rc.conf.
By default all tmpfs that have device nodes are not mounted.
first, mount root and run the various disk providers. Add swap and
check the remaining file systems after that.
This breaks the dependency cycle for lvm, which needs writeable /dev.
Depend on rndctl in cgd.
If set to yes, block-type swap partitions will be deleted upon shutdown.
This can be useful if swapping onto a RAIDframe device, but may cause
unnecessary delays during shutdown for the general case, so it's
disabled by default.
Should resolve [bin/14433] and [kern/14769].
