[elastic-agent] cloud restrict elastic-agent setup

[simitt]

For backwards compatibility on cloud, ensure that the container cmd only triggers the elastic-agent setup if any of the configuration files for the agent are present.

[elasticmachine]

Pinging @elastic/agent (Team:Agent)

[ruflin]

Will this make testing without a container or in the default container harder? I wonder if we could have some logic that it is always executed by default but if a certain condition matches, it is skipped.

[simitt]

This will not impact the default container behavior, it is only in combination with the cloud setup.

[blakerouse]

The container command already skips the enrollment and boot strapping if fleet.yml is present (unless its forced by the environment variable)? Is this different than that?

[mostlyjason]

Tagging @ph track this one and adding to iteration board

[simitt]

@blakerouse yes, because for backwards compatibility to older ECE versions (which will not support the agent and fleet setup), there shouldn't be any notion of enrolling the elastic agent etc; there won't be a fleet.yml present when first called.
The way we can figure this out is to not run a enroll/setup command when ELASTIC_AGENT_CLOUD=false or unset and no configuration file is provided. I'll create a PR for this in a bit.