added dns record already exists handling

dnsapi/dns_plesk.sh

@@ -101,7 +101,12 @@ function add_txt_record() {
     plesk_api "$request"
 
   if ! _contains "${response}" '<status>ok</status>'; then
+    # check if record already exists
+    if ! _contains "${response}" '<errcode>1007</errcode>'; then
       return 1
+    else
+      return 0
+    fi
   fi
     return 0
 }