When the number of account/container or container/object replicas are
different, Swift had a few misbehaviors. This commit fixes them.
* On an object PUT/POST/DELETE, if there were 3 object replicas and
only 2 container replicas, then only 2 requests would be made to
object servers. Now, 3 requests will be made, but the third won't
have any X-Container-* headers in it.
* On an object PUT/POST/DELETE, if there were 3 object replicas and 4
container replicas, then only 3/4 container servers would receive
immediate updates; the fourth would be ignored. Now one of the
object servers will receive multiple (comma-separated) values in the
X-Container-* headers and it will attempt to contact both of them.
One side effect is that multiple async_pendings may be written for
updates to the same object. They'll have differing timestamps,
though, so all but the newest will be deleted unread. To trigger
this behavior, you have to have more container replicas than object
replicas, 2 or more of the container servers must be down, and the
headers sent to one object server must reference 2 or more down
container servers; it's unlikely enough and the consequences are so
minor that it didn't seem worth fixing.
The situation with account/containers is analogous, only without the
async_pendings.
Change-Id: I98bc2de93fb6b2346d6de1d764213d7563653e8d
6ff644b945