ReplicatedPG: clear osd op reply output for writes

ReplicatedPG: clear osd op reply output for writes

Since the vector of OSDOps used by the reply is the same
as the one processed by do_osd_ops() now, any output data
needs to be cleared for writes. To be compatible with current behavior,
allow writes that aren't applying anything or have failed to return data
still.

Add a new parameter to the MOSDOpReply constructor to determine
whether the output data should be cleared. Clear it for successful
writes, and remove a redundant result < 0 -> result > 0 check in the
process.  This was caught by ceph_test_cls_hello and its
writes_dont_return_data method.

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