[PATCH 1/2] return status from set_data_mode

[Chris Brannon]

> return the value of self._conn.send_command() in set_data_mode()
> This change is based on a patch to opentts by Mesar Hameed to allow clients t
> o see if the
> data mode has been successfully set.

+1 on both of these.

Most (possibly all) of the set_* methods of SSIPClient don't return anything.
They just call send_command, ignoring its return value.
Should they return something?  If so, what should it be?

-- Chris