Fix boot failure in Dracut scripts.

mount-zfs.sh script incorrectly parsed results from zpool list.  Correct
bootfs attribute was only found on systems with a single pool or where
the bootable pool's name alphabetized to before all other pool names.
Boot failed when the bootable pool's name came after other pools
(IE 'rpool' and 'mypool' would fail to find bootfs on rpool.)

Patch correctly discards pools whose bootfs attribute is blank ('-').

Signed-off-by: Zachary Bedell <zac@thebedells.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #402

dracut/90zfs/mount-zfs.sh.in

@@ -18,13 +18,13 @@ case "$root" in
 
 			# Might be imported by the kernel module, so try searching before
 			# we import anything.
-			zfsbootfs=`zpool list -H -o bootfs | sed 'q'`
+			zfsbootfs=`zpool list -H -o bootfs | sed -n '/-/ !p' | sed 'q'`
 			if [ "$?" != "0" ] || [ "$zfsbootfs" = "" ] || \
 				[ "$zfsbootfs" = "no pools available" ] ; then
 				# Not there, so we need to import everything.
 				info "ZFS: Attempting to import additional pools."
 				zpool import -N -a ${ZPOOL_FORCE}
-				zfsbootfs=`zpool list -H -o bootfs | sed 'q'`
+				zfsbootfs=`zpool list -H -o bootfs | sed -n '/-/ !p' | sed 'q'`
 				if [ "$?" != "0" ] || [ "$zfsbootfs" = "" ] || \
 					[ "$zfsbootfs" = "no pools available" ] ; then
 					rootok=0