virhostdevtest: Check for integer retval in more verbose way

virhostdevtest: Check for integer retval in more verbose way

There are few functions called from the test which return an
integer but their retval is compared as if it was a pointer.
Now, there is nothing wrong with that from machine POV, but
from readability perspective it's wrong.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>