resources update methods

[treywelsh]

Update methods doesn't work all the same way there is some refactoring to do.

Some of them use Partial and SetPartial methods, some others not.
As a side note, SetPartial is deprecated in later version of terraform SDK (but we don't use the SDK for now): https://www.terraform.io/docs/extend/guides/v2-upgrade-guide.html#removal-of-helper-schema-resourcedata-setpartial

Some of them don't call the read method at the end of the update.

I modified the VM update method in a previous PR (NIC update) but I still have some points to figure out around partial update of the state in case of update failure

[treywelsh]

Some providers seems to remove Partial and SetPartial calls, some other keeps Partial calls only.

Calling Partial may have an impact in case of an error during an update operation, see doc linked above and this issue for more details.

From my understanding, a diff may be applied to the state, even in case of an error during update operation, for values that aren't Set in Read resource operation.
There are some attributes in this provider that could be impacted but for now I don't see any case were this would be legitimate to keep a Partial call.

For instance VM context should be impacted (or some other attributes only used at VM creation time), but to me, it seems to be an other problem, we should just read it or forbid the user to update it with a check.
This issue is more appropriated for this discussion: it point diff applied in state with no effect on the cloud provider side.

The PR I proposed for now remove all Partial and SetPartial calls.