tests: Use stat -c

Change all occurrences of stat --format and stat --printf to stat -c
so that the tests work correctly on BusyBox systems.

Signed-off-by: Ari Sundholm <ari@tuxera.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/generic/215

@@ -53,8 +53,8 @@ echo
 echo "creating test file"
 dd if=/dev/zero of=$testfile count=4096
 
-mtime1=`stat --printf="%Y" $testfile`
-ctime1=`stat --printf="%Z" $testfile`
+mtime1=`stat -c "%Y" $testfile`
+ctime1=`stat -c "%Z" $testfile`
 
 sleep 2
 
@@ -65,8 +65,8 @@ $XFS_IO_PROG -f 		\
 	-c 'mwrite 0 4096'	\
 	$testfile | _filter_xfs_io_unique
 
-mtime2=`stat --printf="%Y" $testfile`
-ctime2=`stat --printf="%Z" $testfile`
+mtime2=`stat -c "%Y" $testfile`
+ctime2=`stat -c "%Z" $testfile`
 
 let mtime_diff=$mtime2-$mtime1
 let ctime_diff=$ctime2-$ctime1