qemu.tests: add new test block_hotplug_check

changes from v1:
    add windows guest support;

changes from v2:
    remove extra image params in cfg and generate it by script
    fix issue that failed to check device id at rhel7 host
    limited test on Host_RHEL
changes form v3:
    fix typo error
    fix pep8 isssue

Signed-off-by: Xu Tian <xutian@redhat.com>
Merge pull request #12 from xutian/block_hotplug_check

qemu.tests: add new test block_hotplug_check