re-adding a replacement into a pool of mirrors

[Randy Bush]

> 1. zpool replace -f tank da1s3

# zpool replace -f tank da1s3
cannot replace da1s3 with da1s3: permission denied

> 2. zpool offline tank da1s3 ; zpool online tank da1s3

# zpool offline tank da1s3
cannot offline da1s3: no valid replicas

but tried anyway

# zpool online tank da1s3
warning: device 'da1s3' onlined, but remains in faulted state
use 'zpool replace' to replace devices that are no longer present

        NAME        STATE     READ WRITE CKSUM
        tank        DEGRADED     0     0     0
          mirror    DEGRADED     0     0     0
            da0s3   ONLINE       0     0     0
            da1s3   REMOVED      0     0     0

randy