(#9329) Disable agent daemonizing on Windows

Running puppet agent on Windows with the default set of options fails
because the win32-process gem doesn't really support fork (it
re-executes the parent program, but doesn't preserve the parent
context), and then it fails to setsid as this call is not implemented
by the ruby runtime.

But the bigger issue is that Windows services are the preferred way to
run daemon processes. For this release, we will not be providing the
code to run puppet agent as a service, though we have verified that
puppet will run as a service using a third-party service wrapper,
nssm.

This commit changes the daemonize option to default to false on
Windows, so that the typical 'puppet agent' command does the right
thing. And if the daemonize option is set to true on Windows, it will
report an error.