tests: Add a small sleep in FT run_roams()

tests: Add a small sleep in FT run_roams()

time.sleep() in run_roams() is required because the target AP sets the
key once the station was associated. There are races, when the station
processes the (Re)Association Response frame AND the test suite starts
FT_DS before the AP processes its local confirmation and thus
wpa_auth_sm_event(ASSOC_FT). Therefore, the ActionFrame will be lost, as
the AP driver is missing the key.

Since this is this speed is highly synthetic, wait a few milliseconds
before roaming back.

Signed-off-by: Michael Braun <michael-dev@fami-braun.de>