Firmware seems to be getting into odd state in host_roaming mode 2
when hostscan is used without join command, so try to fix this by
re-joining the current AP. This does not actually trigger a new
association if the current AP is still in the scan results.

This makes background scans (iwlist wlan0 scan) not to break data
connection when in host_roaming 2 mode, e.g., when using wpa_supplicant.
Signed-off-by: NJouni Malinen <jkmaline@cc.hut.fi>
Signed-off-by: NJeff Garzik <jgarzik@pobox.com>