Introduce qemu guest agent tests for windows guests

The original qemu guest agent tests are designed for linux guest only, this pullreq tries to make them work for windows guests.

Note, Fedora doesn't ship a qemu-guest-agent program for windows, so I have to use a program shipped with CentOS (which is forked from RHEL).

Note2, Hibernate (S4) can't work with guest agent now for bug https://bugzilla.redhat.com/show_bug.cgi?id=888694 , thus the check_suspend test will fail as expected.