Mount cd by label

The idea is that a system may have multiple CD drives (real or virtual), mfsbsd media may be in a drive other than cd0 or cd1, and also cd0 or cd1 may happen to have some other media loaded.
So, if we want to be sure that mfsbsd is mounted in /cdrom, the safest way to do that is mount by label.

The only case I am not sure about is when hc-install is used without mfsbsd media.
But I guess that in that case we generally do not expect anything useful on a CD.
If there is a need to mount a custom CD, then probably that would be best done explicitly / manually from a shell prompt.