Improve UX for commands annotated with updateAPIConfig

[mandopaloooza]

When a command upgrade prepare and upgrade complete (commands with updateAPIConfig annotation) is run before the sdpctl configuration is initialized, it prints the following warning:

It is strongly adviced that you upgrade your appliance to a supported version before executing any sdpctl command. Executing sdpctl commands on an unsupported API version can have serious unforseen consequenses.
Minimum supported API version: 17
Currently using API version: 0

sdpctl reads the key api_version in the config to extract the current API version. This configuration key is only initialized when the user authenticates sdpctl. I changed the orders of the warning printer after there is an attempt to signin.

[thomascellerier]

I'm still not sure this warning makes sense as we always hit it when running in non interactive mode with env variables.
If the current API version is 0 we can auto discover the API version like we did in the old upgrade script, without printing a warning.

[kajes]

I'm fine merging this and we should probably do a release with this fix fairly quickly.