Make sure that the error in ADDRMAP events is well-formed

"error=Unable to launch resolve request" is not a nice thing to tell
the controller.  Bugfix on 0.2.0.19-alpha (c11c48fc).

changes/addrmap_error

@@ -0,0 +1,5 @@
+  o Minor bugfixes (controller):
+    - The ADDRMAP command can no longer generate an ill-formed error
+      code on a failed MAPADDRESS. It now says "internal" rather than
+      an English sentence fragment with spaces in the middle. Bugfix on
+      Tor 0.2.0.19-alpha.

src/or/control.c

@@ -2943,7 +2943,7 @@ handle_control_resolve(control_connection_t *conn, uint32_t len,
   send_control_done(conn);
   SMARTLIST_FOREACH(failed, const char *, arg, {
       control_event_address_mapped(arg, arg, time(NULL),
-                                   "Unable to launch resolve request");
+                                   "internal");
   });
 
   SMARTLIST_FOREACH(args, char *, cp, tor_free(cp));