Revert "Fix: wrong condition on startup for low-activity streams"

This reverts commit d3aac146d0800fe9820d51e5b9fa52e7543c1237.

Acked-by: Julien Desfossez <julien.desfossez@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>
Fix: only create UST metadata on start trace

Fixes #739

Acked-by: Julien Desfossez <julien.desfossez@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>