Add a missing free in parsing an :auto port

Fixes bug 18374; bugfix on 0.2.3.3-alpha.

changes/bug18374

@@ -0,0 +1,3 @@
+  o Minor bugfixes (configuration):
+    - Fix a tiny memory leak when parsing a port configuration ending in
+      ":auto". Fixes bug 18374; bugfix on 0.2.3.3-alpha.

src/or/config.c

@@ -6373,6 +6373,7 @@ parse_port_config(smartlist_t *out,
         tor_free(addrtmp);
         goto err;
       }
+      tor_free(addrtmp);
     } else {
       /* Try parsing integer port before address, because, who knows?
          "9050" might be a valid address. */