convert all defaults to be quoted in docker-distribution role

roles/docker-distribution/defaults/main.yml

@@ -3,29 +3,29 @@
 #
 
 # where to put the config.yml on the remote machine
-conf_path: /etc/docker-distribution/registry/config.yml
+conf_path: "/etc/docker-distribution/registry/config.yml"
 
 # Cert information to place certificate files on system
 cert:
-  private_path: PRIVATE_PATH_TO_CERT_DIR
+  private_path: "PRIVATE_PATH_TO_CERT_DIR"
   dir: "/etc/pki/docker/{{ ansible_fqdn }}:5000"
-  src_name: ca.crt
+  src_name: "ca.crt"
-  src_key_name: ca.key
+  src_key_name: "ca.key"
-  dest_name: ca.crt
+  dest_name: "ca.crt"
-  dest_key_name: ca.key
+  dest_key_name: "ca.key"
 
 # Config directives
 tls:
   enabled: False
-  certificate: PATH_TO_CERT
+  certificate: "PATH_TO_CERT"
-  key: PATH_TO_KEY
+  key: "PATH_TO_KEY"
 log:
   fields:
-    service: registry
+    service: "registry"
 storage:
   cache:
-    layerinfo: inmemory
+    layerinfo: "inmemory"
   filesystem:
-    rootdirectory: /var/lib/registry/
+    rootdirectory: "/var/lib/registry/"
 http:
-  addr: :5000
+  addr: ":5000"