utils: make isOvirtNode always return a boolean

Up until now, if the first condition that isOvirtNode was False, the
function would return a list (generated by glob). This patch fixes
that as all the consumers use this function for its truthiness.

Change-Id: I46bc5b315bd28f260e3c7c1eb61d3ec947f74d76
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28898
Reviewed-by: Dan Kenigsberg <danken@redhat.com>