Bug where pxebr was checking for link state UP before the subinterface
was added to the bridge. Moved the check to be after. Added a short
sleep in between issuing the link up and checking link status.
JIRA: OCTO-109
Change-Id: I7f782a35adf49b0da675e932d109c41b26016a5b Signed-off-by: Tim Rozet <trozet@redhat.com>