windows, ovn-nbctl: Add service_start call inside the server loop

windows, ovn-nbctl: Add service_start call inside the server loop

Currently all ovn-nbctl (daemon) tests are failing due to the missing
call to `service_start` which is required on Windows.

Windows lacks fork so we need to pass all arguments, so we can spawn a new
process and interpret it properly when calling `service_start`.

Signed-off-by: Alin Gabriel Serdean <aserdean@ovn.org>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Co-authored-by: Ben Pfaff <blp@ovn.org>
Acked-by: Anand Kumar <kumaranand@vmware.com>