setHeatingSetpoint fails (or is ignored) when thermostat is in 'off' mode

[simondsmason]

Related to the issue where my Ecobee apparently ignored the setThermostatMode command this brought up a second issue:

When the Ecobee thermostat is in 'off' mode, attempting to change to 'heat' mode via setThermostatMode('heat') fails silently. The thermostat remains in 'off' mode, and any subsequent setpoint change commands are ignored because Ecobee ignores setpoint changes when the system is in 'off' mode.

In theory the system should not be in OFF mode when a set point is changed but that was not the case on my system this morning.

Steps to Reproduce

1. Thermostat is in 'off' mode
2. Hubitat Thermostat Controller calls setHeatingSetpoint(71)
3. Driver calls setThermostatMode('heat')
4. Parent app's setMode() sends API request to Ecobee
5. API request fails (returns non-zero status code)
6. Thermostat remains in 'off' mode
7. Driver then calls setHeatingSetpoint(71)
8. Setpoint change is sent via updateThermostatSetpoints() → parent.setHold()
9. Ecobee ignores the setpoint change because system is still in 'off' mode

Possible solutions - add code in to set point code to check that it is in an acceptable mode? Resolve an issue when it is out of alignment?