preciousblock "blockhash"
Treats a block as if it were received before others with the same work.
A later preciousblock call can override the effect of an earlier one.
The effects of preciousblock are not retained across restarts.
Arguments:
1. blockhash (string, required) the hash of the block to mark as precious
Examples:
> elements-cli preciousblock "blockhash"
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "preciousblock", "params": ["blockhash"] }' -H 'content-type: text/plain;' http://127.0.0.1:7041/
