critical path: Clean up link list of content provider

critical path: Clean up link list of content provider

The link cache was not used because it was written to one map, but read
from another. So links were computed every time

Change-Id: Id3533034be15e1e974160338d9d5e56bda84992e
Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>
Reviewed-on: https://git.eclipse.org/r/72761
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>