Forget passwords while stopping persistent connections

In case of persistent connections, openvpn.exe is still running
after a disconnect, and another user can restart it without needing
credentials using cached passwords. Avoid this by sending
"forget-passwords" to the management interface before disconnect.

Only persistent connections are affected.

In openvpn.exe versions >= 2.5.8, this will also clear cached
auth_token, if present.

Signed-off-by: Selva Nair <selva.nair@gmail.com>

openvpn.c

@@ -1809,6 +1809,7 @@ DisconnectDaemon(connection_t *c)
     {
         if (c->manage.connected > 1) /* connected and ready for input */
         {
+            ManagementCommand(c, "forget-passwords", NULL, regular);
             ManagementCommand(c, "hold on", NULL, regular);
             ManagementCommand(c, "signal SIGHUP", NULL, regular);
         }