runltp: suppress the out message when creating loop device

Acked-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
diff --git a/runltp b/runltp
index 63c625f..c8a2e20 100755
--- a/runltp
+++ b/runltp
@@ -956,7 +956,7 @@
 create_block()
 {
     #create a block device
-    dd if=/dev/zero of=${TMP}/test.img bs=1kB count=20480
+    dd if=/dev/zero of=${TMP}/test.img bs=1kB count=20480 >/dev/null 2>&1
     if [ $? -ne 0 ]; then
         echo "Failed to create loopback device image, please check disk space and re-run"
         return 1