tests: nodedev: switch all test macros to accept a filename

tests: nodedev: switch all test macros to accept a filename

Rather than specifying a UUID string to some test macros, just pass a
filename to an xml definition. This helps work toward unifying the test
macros and making it more maintainable.

Signed-off-by: Jonathon Jongsma <jjongsma@redhat.com>
Reviewed-by: Laine Stump <laine@redhat.com>