nodedev: refactor tests to support mdev undefine
nodedev: refactor tests to support mdev undefine

mdevctl 'stop' and 'undefine' commands take the same uuid parameter, so
refactor the test infrastructure to share common implementation for both
of these commands. The 'undefine' command will be introduced in a
following patch.

Signed-off-by: Jonathon Jongsma <c7254805a17bd5c41e24c3a278fcbf3afcdfb0fa@redhat.com>
Reviewed-by: Erik Skultety <2c14d38fa47c8799f1b9c16280abe27f8edfec6e@redhat.com>

zippy2/libvirt,libvirt/libvirt,nertpinx/libvirt,zippy2/libvirt,nertpinx/libvirt,zippy2/libvirt,jfehlig/libvirt,libvirt/libvirt,jfehlig/libvirt,olafhering/libvirt,nertpinx/libvirt,crobinso/libvirt,crobinso/libvirt,libvirt/libvirt,zippy2/libvirt,crobinso/libvirt,olafhering/libvirt,olafhering/libvirt,jfehlig/libvirt,nertpinx/libvirt,jfehlig/libvirt,libvirt/libvirt,crobinso/libvirt,nertpinx/libvirt,olafhering/libvirt