unlock dns cache entries with a function call instead of a variable fiddle

lib/ftp.c

@@ -1215,7 +1215,8 @@ CURLcode ftp_use_port(struct connectdata *conn)
   }
 
   if(h)
-    h->inuse--; /* when we return from here, we can forget about this */
+    /* when we return from here, we can forget about this */
+    Curl_resolv_unlock(h);
 
   if ( h || sa_filled_in) {
     if( (portsock = socket(AF_INET, SOCK_STREAM, 0)) >= 0 ) {
@@ -1479,7 +1480,7 @@ CURLcode ftp_use_pasv(struct connectdata *conn,
                             &conninfo,
                             connected);
 
-  addr->inuse--; /* we're done using this address */
+  Curl_resolv_unlock(addr); /* we're done using this address */
 
   /*
    * When this is used from the multi interface, this might've returned with