stats: Document config parameters
commite13cc5d0b40df8f4882f630e2025ba378593490d
authorEric Blake <eblake@redhat.com>
Wed, 31 Jul 2019 20:36:56 +0000 (31 15:36 -0500)
committerEric Blake <eblake@redhat.com>
Wed, 31 Jul 2019 20:45:51 +0000 (31 15:45 -0500)
treed8dec4810bf344384b1fe1c2fe2eddf6ce065e54
parent680960977425623c0449505e1b3def153bb1cf02
stats: Document config parameters

Make 'nbdkit --help --filter=stats null' give more details about the
stats filter.  Missed with the introduction of the filter.

Fixes: fa0585f1
Signed-off-by: Eric Blake <eblake@redhat.com>
filters/stats/stats.c