Fixing swap1_stop

["Ian D. Leroux" <idleroux%fastmail.fm@localhost>]

For the last year or so I've been carrying a set of local patches
to /etc/rc.d/swap1, /etc/defaults/rc.conf and the attendant
documentation.  The patches stop swap1_stop from blindly unmounting
a tmpfs-mounted /dev/while the system is still running multi-user.  I
was about to submit a PR to try to get the patches into the tree (so
that I don't have to tip-toe around them every time I update my base
system) when I discovered that ... I already did: bin/51019.

The development of the patches is discussed in the thread starting at:
https://mail-index.netbsd.org/current-users/2016/03/13/msg029029.html

Could someone take a look and let me know what still needs to be
improved before they can be committed?  I'd like to get this sorted out
before I go looking for more windmills at which to tilt ...

Thanks,

--
IDL