(#6793) Fix incorrect mount name munging

The trailing slashes were removed by running File.expand_path. This
works if the destination mountpoint is an actual filesystem path but
does not work if we describe a special filesystem like swap.

According to the manpage the mountpoint should be specified as "none"
for swapdevices and `File.expand_path("none")` adds the current working
directory to the path.

Remove any trailing slashes with a regex instead running `expand_path`.
Make sure that we do not trim a trailing slash if we specify the root
directory `/`
(#6409) Dont use invalid values in type_spec

The type_spec uses the mount type as an example in a lot of spec tests.
Unfortunately it uses example values that are now invalid for the mount
type.

The atboot property only accepts :yes and :no now, because these are the
only valid options in /etc/vfstab [1].

[1] http://docs.oracle.com/cd/E19455-01/805-7228/6j6q7uev3/index.html