Fix shell condition for checking docker cert valid period

Change-Id: Ie6dd8313be8874360fa8d6253e1a0fd666698d5d
Related-Prod: PROD-34739
diff --git a/config-drive/mirror_config.yaml b/config-drive/mirror_config.yaml
index c4d24ba..d4adbd7 100644
--- a/config-drive/mirror_config.yaml
+++ b/config-drive/mirror_config.yaml
@@ -14,7 +14,7 @@
 - &mirror_config |
     function docker_ca_wa(){
       crt="/var/lib/docker/swarm/certificates/swarm-node.crt"
-      if ! $(openssl x509 -checkend 86400 -noout -in ${crt}); then
+      if openssl x509 -checkend 86400 -noout -in ${crt}; then
         echo "WARNING: swarm CA not expired yet.Something other wrong with docker"
         echo "WARNING: docker CA WA not applied"
         exit 1