Change the behavior of load_firmware and add new get_firmware command

[alonagetzler]

@AlonSaggie :
Change Load Firmware to also update the 'Version' attribute', so
orchestration will have the details of the current installed version.

Add a 'Get Firmware' function to check the installed version on the
device and update the attribute, to enable a refresh of the attribute
value.

related to #3

[alonagetzler]

@AlonSaggie - I think you meant the "OS Version" attribute on the root model and not the "Version" attribute which is associated with the sub-resources. Why don't you just use Autoload to update the value of this attribute (together with other device attributes)?

[AlonSaggie]

@alonagetzler, your comment about the "OS Version" is correct.

As part of the Setup orchestration workflow we'd like to check wether the OS Version is correct, and if not, upgrade the device's firmware. Auto-loading the device is an overkill and generally speaking it's not something we'd like to perform at the beginning of each reservation.

Regardless, IMHO I think that it should be the 'Load firmware' command's responsibility to update the relevant attribute once it is being used to upgrade a device, that way we have an atomic operation that takes care of the data integrity of our data model. You don't want the orchestration command to implement a 'Set Attribute' command following the 'Load firmware' command - it makes the flow more complex.