Save `QINIU_CDN_DOMAIN` only when defined

deploy/qiniu.sh

@@ -36,12 +36,12 @@ qiniu_deploy() {
     _savedomainconf QINIU_SK "$QINIU_SK"
   fi
 
-  if [ -z "$QINIU_CDN_DOMAIN" ]; then
-    QINIU_CDN_DOMAIN="$_cdomain"
+  if [ "$QINIU_CDN_DOMAIN" ]; then
+      _savedomainconf QINIU_CDN_DOMAIN "$QINIU_CDN_DOMAIN"
+  else
+      QINIU_CDN_DOMAIN="$_cdomain"
   fi
 
-  _savedomainconf QINIU_CDN_DOMAIN "$QINIU_CDN_DOMAIN"
-
   ## upload certificate
   string_fullchain=$(sed 's/$/\\n/' "$_cfullchain" | tr -d '\n')
   string_key=$(sed 's/$/\\n/' "$_ckey" | tr -d '\n')