Make the UNUSUAL warning in plugin-bcli depend on rpcclienttimeout

[hMsats]

If a user has set rpcclienttimeout to a higher value than the default 60 seconds, it seems logical that the corresponding UNUSUAL warning in bcli_finished when a rpc request takes longer than 10 seconds, should also increase proportionally.

This is how I've implemented it (in bcli_finished, plugin-bcli) but if this change is desired, I leave it to the developers to implement it in the proper manner.

        u64 msec_unusual;
 
        /* For default rpcclienttimeout=60, "msec_unusual" should equal 10 seconds -> 10000 msec */
        msec_unusual=(u64) (bitcoind->rpcclienttimeout/6*1000);
        if (msec > msec_unusual)
                plugin_log(bcli->cmd->plugin, LOG_UNUSUAL,
                           "bitcoin-cli: finished %s (%"PRIu64" msec)",
                           bcli_args(tmpctx, bcli), msec);