* fix(volume): return an error instead of 201 when a write lands on no volume
ReplicatedWrite only writes locally when this server holds the volume.
For a volume id no server holds, the master lookup returns no locations,
so the write went nowhere and the upload still got 201 Created. The same
happened for a type=replicate write to a server without the volume, so
the primary, or the S3 chunk fan-out, counted a replica that was never
written.
A server without the volume still forwards the write to the replicas the
master lists. When there is nothing to forward to, fail with "volume N
not found on host:port". PostHandler returns that as 500, the status the
Rust volume server already returns here, and uploaders re-assign on 5xx.
Fixes#6609
* volume: reuse Store.HasVolume, drop issue ref from test comment
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Co-authored-by: Chris Lu <chris.lu@gmail.com>