adtrustinstance: Make sure smb.conf exists

The 'net' command fails unless smb.conf exists. Touch
the file prior to any 'net' call to make sure we do not crash
for this very reason.

https://fedorahosted.org/freeipa/ticket/5687

Reviewed-By: Martin Basti <mbasti@redhat.com>

ipaserver/install/adtrustinstance.py

@@ -520,6 +520,11 @@ class ADTRUSTInstance(service.Service):
         os.write(tmp_fd, conf)
         os.close(tmp_fd)
 
+        # Workaround for: https://fedorahosted.org/freeipa/ticket/5687
+        # We make sure that paths.SMB_CONF file exists, hence touch it
+        with open(paths.SMB_CONF, 'a'):
+            os.utime(paths.SMB_CONF, None)
+
         args = [paths.NET, "conf", "import", tmp_name]
 
         try: