ipwrapperTests: prevent infinite stuck of iterator

Sometimes, ipwrapper monitor.start() is not fast enough and it's
returned before it's proper started and listening. In this case, monitor
doesn't catch the first created device and iterator.next() stuck
forever.

I included quick sleep() fix, to prevent this problem until we get new
netlink-based event monitor.

Change-Id: Iec49f21c76a1cd9d02e3fb1f36a4d4e4de7f057e
Signed-off-by: Petr Horáček <phoracek@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/36121
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>