If /dev/osd* devices are shuffled because more devices
where added, and/or login order has changed. It is hard to
mount the FS you want.
Add an option to mount by osdname. osdname is any osd-device's
osdname as specified to the mkfs.exofs command when formatting
the osd-devices.
The new mount format is:
OPT="osdname=$UUID0,pid=$PID,_netdev"
mount -t exofs -o $OPT $DEV_OSD0 $MOUNTDIR
if "osdname=" is specified in options above $DEV_OSD0 is
ignored and can be empty.
Also while at it: Removed some old unused Opt_* enums.