Interactive service: do not set target desktop for openvpn.exe process

Setting desktop as "winsta0\default" does not work when run from a
non-interactive session which may not have access to it. Leave this
blank to let the system select an appropriate value.

Tests show that "winsta0" gets selected when run interactively
(eg., using the GUI) and a service-specific temporary station gets created
when run from task scheduler.

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

src/openvpnserv/interactive.c

@@ -1868,7 +1868,6 @@ RunOpenvpn(LPVOID p)
     }
 
     startup_info.cb = sizeof(startup_info);
-    startup_info.lpDesktop = L"winsta0\\default";
     startup_info.dwFlags = STARTF_USESTDHANDLES;
     startup_info.hStdInput = stdin_read;
     startup_info.hStdOutput = stdout_write;