Prevent virt_wifi connect request interference.

If multiple connection requests come into the device, the driver used to
update the MAC address it was attempting to connect to before checking
if it can schedule a connection attempt. One connection request could
this way cause the mac address to change of another connect request in
flight.

Bug: 116027983
Change-Id: I3ebd8dfe25679bb8c9726af938dfb5d5dc0e210a
Signed-off-by: A. Cody Schuffelen <schuffelen@google.com>
Acked-by: Greg Hartman <ghartman@google.com>