Reimplement SetOmap in terms of a new SetOmap function on the WriteOp.
Now the actions of the write op can start to be atomically chained the
way WriteOps are supposed to.
Signed-off-by: John Mulligan <jmulligan@redhat.com>
The WriteOp type will manage librados write operations and the
corresponding functions that ceph names like rados_write_op_*.
Signed-off-by: John Mulligan <jmulligan@redhat.com>