dirmngr: Fix LDAP port parsing.

* dirmngr/misc.c (host_and_port_from_url): Fix bad port parsing and a
segv for a missing slash after the host name.
--

Reportted-by: Tomas Mraz
GnuPG-bug-id: 4230
Signed-off-by: Werner Koch <wk@gnupg.org>

dirmngr/misc.c

@@ -515,7 +515,7 @@ host_and_port_from_url (const char *url, int *port)
   if ((p = strchr (buf, '/')))
     *p++ = 0;
   strlwr (buf);
-  if ((p = strchr (p, ':')))
+  if ((p = strchr (buf, ':')))
     {
       *p++ = 0;
       *port = atoi (p);