mgr/nfs: add known_cluster_ids to generalize nfs cluster id fetching
The changes to the nfs module in
8c711afc are working but when I began
writing more test automation I found a few more places in the
export-configuration code path relying on the orchestration module
only. This change generalizes the logic to source nfs clusters from
orchestration when it's enabled but from the .nfs pool when
orchestration is disabled. It then uses that call when loading
the exports cache on the ExportMgr object.
Signed-off-by: John Mulligan <jmulligan@redhat.com>