Venstar: split away and schedule settings calls (#13046)

Venstar: split away and schedule settings calls (#13046)

Separate Venstar thermostat API calls to change the away mode or
schedule-enabled mode so that the POST to the thermostat's REST
API settings endpoint contains only one of these two params.

Newer ColorTouch thermostat firmwares will reject any POSTs to the
settings endpoint that include the 'schedule' parameter when the
thermostat is currently in AWAY mode, regardless of the value
passed for 'schedule'.  This had the effect of preventing the
OpenHab binding from un-setting away mode.

Signed-off-by: David Eberhart <git@daveeberhart.com>