altos: Wait for BT disconnect before sending command

If AltosDroid manages to connect to the BT module before we've
configured it, we won't be able to talk to it as we can't force the
module to ignore connection attempts. Wait for AltosDroid to give up
and let us configure the device. Eventually, we'll manage, if
AltosDroid's delay interval is longer than the time it takes to
configure the unit.

Signed-off-by: Keith Packard <keithp@keithp.com>