xfstests: avoid blkid cache with -c /dev/null not -p

The addition of "-p" to blkid calls broke xfstests
on older systems where this was not supported.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>

common

@@ -47,7 +47,7 @@ rm -f $tmp.list $tmp.tmp $tmp.sed
 # Autodetect fs type based on what's on $TEST_DEV
 if [ "$HOSTOS" == "Linux" ]
 then
-    export FSTYP=`blkid -p -s TYPE -o value $TEST_DEV`
+    export FSTYP=`blkid -c /dev/null -s TYPE -o value $TEST_DEV`
 else
     export FSTYP=xfs
 fi