Jaeger tags for injected agent are only added if a single container is present

[TBBle]

I'm specifically looking at func container in https://github.com/jaegertracing/jaeger-operator/blob/master/pkg/inject/sidecar.go.

The flow appears to be intended to inject a bunch of tags from the pod info, and if a single container is present, include a tag about the container.

However, the entire set of tags is only added in a single-container setup.

This looks like a trivial mistake in #648.

[TBBle]

I don't have an immediate fix for it, but I suspect the 'only one container' logic will also fail if called from UpdateSidecar, as it the jaeger-agent side-car will be seen as a second container.

[jpkrohling]

Nice catch!