Do not import a pool that the kernel automatically imported

This works around the following upstream issue:
https://github.com/zfsonlinux/zfs/issues/714

Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>

defaults/initrd.scripts

@@ -654,7 +654,7 @@ startVolumes() {
 	
 	if [ "${USE_ZFS}" = '1' ]
 	then
-		if [ -z "${ZFS_POOL}" ];
+		if [ -z "${ZFS_POOL}" ]
 		then
 			good_msg "Importing ZFS pools"
 
@@ -667,15 +667,21 @@ startVolumes() {
 				bad_msg "Imported ZFS pools failed"
 			fi
 		else
-			good_msg "Importing ZFS pool ${ZFS_POOL}"
 
-			/sbin/zpool import -N "${ZPOOL_FORCE}" "${ZFS_POOL}"
+			if [ "$(zpool list -H -o name ${ZFS_POOL} 2>&1)" = "$ZFS_POOL" ]
-
-			if [ "$?" = '0' ]
 			then
-				good_msg "Importing ${ZFS_POOL} succeeded"
+				good_msg "ZFS pool ${ZFS_POOL} already imported"
 			else
-				bad_msg "Importing ${ZFS_POOL} failed"
+				good_msg "Importing ZFS pool ${ZFS_POOL}"
+
+				/sbin/zpool import -N "${ZPOOL_FORCE}" "${ZFS_POOL}"
+
+				if [ "$?" = '0' ]
+				then
+					good_msg "Importing ${ZFS_POOL} succeeded"
+				else
+					bad_msg "Importing ${ZFS_POOL} failed"
+				fi
 			fi
 		fi
 	fi