nfs: propagate NFS errors of server-side-copy to the client

Motivation:
when server-side-copy with an NFS error, like NOT_SUPP, then we want
this error to be propagated to the client.

Modification:
Update OperationCOPY to map only non NFS errors to EIO.

Result:
proper error handling.

Acked-by: Albert Rossi
Target: master

core/src/main/java/org/dcache/nfs/v4/OperationCOPY.java

@@ -124,7 +124,11 @@ public void process(CompoundContext context, nfs_resop4 result) throws ChimeraNF
                 long n = copyFuture.get(1, TimeUnit.SECONDS);
                 res.cr_resok4.cr_response.wr_count = new length4(n);
             } catch (InterruptedException | ExecutionException e) {
-                LOGGER.error("Copy-offload interrupted: ", Throwables.getRootCause(e));
+
+                Throwable cause = Throwables.getRootCause(e);
+                Throwables.propagateIfPossible(cause, ChimeraNFSException.class);
+
+                LOGGER.error("Copy-offload failed: {}", e.getMessage());
                 res.cr_status = nfsstat.NFSERR_IO;
             } catch (TimeoutException e) {
                 // continue as async copy