flux-resource: fix eventlog --follow

Problem: Commit 852ac6d updated the
`flux resource eventlog` command to use the ResourceJournalConsumer
class, but this dropped support for the `-F, --follow` option, which
is now ignored.

Suppress the journal sentinel event with `-F, --follow`, which prevents
the command from exiting after historical events have been processed.

Fixes #6634

Author: grondo

src/cmd/flux-resource.py

@@ -734,7 +734,9 @@ def eventlog(args):
     evf = EventLogFormatter(
         format=args.format, timestamp_format=args.time_format, color=args.color
     )
-    consumer = ResourceJournalConsumer(h, include_sentinel=True).start()
+    # The sentinel event is only used if we're not following the eventlog:
+    sentinel = not args.follow
+    consumer = ResourceJournalConsumer(h, include_sentinel=sentinel).start()
     while True:
         event = consumer.poll()
         if event is None or event.is_empty():