docker api: use helper to parse context docker endpoint metadata

[crazy-max]

follow-up https://github.com/docker/buildx/issues/1249#issuecomment-1205162020

Use docker.EndpointFromContext to parse context docker endpoint metadata.

Also remove dockerapi.NegotiateAPIVersion(ctx) which is already provided by dockerclient.NewClientWithOpts.

Signed-off-by: CrazyMax [email protected]

[crazy-max]

which is already provided by dockerclient.NewClientWithOpts.

Could you point to what you mean by that.

It's ep.ClientOpts() actually my bad: https://github.com/docker/cli/blob/f1615facb1ca44e4336ab20e621315fc2cfb845a/cli/context/docker/load.go#L124

[crazy-max]

PTAL @thaJeztah @tonistiigi