Fix redis install script for centos

Change-Id: Iff2449ce775dc39b34f03b980c380db08472a7a3
Issue-id: CIMAN-14
Signed-off-by: Gary Wu <gary.i.wu@huawei.com>
diff --git a/packer/provision/redis.sh b/packer/provision/redis.sh
index fc8b2a0..c940c0a 100644
--- a/packer/provision/redis.sh
+++ b/packer/provision/redis.sh
@@ -8,7 +8,7 @@
 
 rh_systems() {
     # redis
-    yum install redis
+    yum install -y redis
     systemctl enable redis.service
 }