daemon.at: Make changes for Windows.

Skip some of the tests that uses '--monitor' as an option as
it is not implemented on Windows.

When a 'kill pid' is done on windows (through 'taskkill //F'),
pidfiles are not deleted (because it is force kill), so use
'ovs-appctl exit' instead.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>