osdc/Objecter: add perfcounters for commands

This matches the other counters we maintain for other kinds of ops.

Signed-off-by: Sage Weil <sage@inktank.com>
osdc/Objecter: kick command ops on osd con resets

Resend osd/pg commands on the OSDSession, just as we do with other request
types.

Signed-off-by: Sage Weil <sage@inktank.com>
osdc/Objecter: ping osds for which we have pending commands

As with ops and linger_ops, this ensures we detect connection resets.

Signed-off-by: Sage Weil <sage@inktank.com>
osdc/Objecter: dump command ops

Dump command_ops along with everything else.

Signed-off-by: Sage Weil <sage@inktank.com>
Merge branch 'wip-objecter' into next

Reviewed-by: Josh Durgin <josh.durgin@inktank.com>