rados: add {read,write}_ops to df json

Backport: firefly, dumpling
Signed-off-by: Sage Weil <sage@redhat.com>
rados: fix {read,write}_bytes value

Fill this in with kb * 1024 instead of the ops count.

Backport: firefly, dumpling
Signed-off-by: Sage Weil <sage@redhat.com>
rados: remove {read,write}_kb fields from rados df json output

Redundant.  Do not backport.

Signed-off-by: Sage Weil <sage@redhat.com>
Merge pull request #2214 from ceph/wip-rados-df-json

rados: fix 'rados df --format=json' field names

Reviewed-by: Josh Durgin <josh.durgin@inktank.com>