set_flow_rate throws error when maximum ramp rate != 0

[brubaked]

A maximum ramp rate can be set on Alicat flow controllers. When this ramp rate is set to a non-zero value, the set_flow_rate command throws an error since the current setpoint does not equal the commanded setpoint. TheAlicay _unit_id_LS command returns both the current setpoint and the commanded setpoint. Using this command to verify that the instrument has correctly received the commanded setpoint would allow the set_flow_rate command to work while a maximum flow rate is set.