Make sure that services listen globally (#273)

they need to be made available through reverse proxy and port forwarding anyways
changed in https://jira.kopano.io/browse/KC-1616

Signed-off-by: Felix Bartels <felix@host-consultants.de>

core/defaultconfigs/gateway.py

@@ -5,6 +5,7 @@ import kcconf
 kcconf.configkopano({
     r"/etc/kopano/gateway.cfg":
     {
+        'imap_listen': "0.0.0.0:143",
         'log_file': "-",
         'log_level': "3",
         'tmp_path': "/tmp/gateway/"