sync-once: Fix shellcheck warnings

Tested: Verified the output that echos the rsync command was the same as
before.

Change-Id: I345bb38bb932f78e57279de0301d47bef81a3d72
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/sync-once.sh b/sync-once.sh
index e26d5af..ff9d84a 100644
--- a/sync-once.sh
+++ b/sync-once.sh
@@ -7,7 +7,7 @@
 SYNCLIST=/etc/synclist
 DEST_DIR=/run/media/rwfs-alt/cow
 
-while read l; do
+while read -r l; do
     echo rsync -a -R "${l}" "${DEST_DIR}"
     rsync -a -R "${l}" "${DEST_DIR}"
 done < ${SYNCLIST}