We limit the number of concurrent blob downloads per node and per recovery, but if a user configures too many concurrent recoveries they may run out of per-node download permits which yields the following message:

> Unable to acquire permit to use snapshot files during recovery, this recovery will recover index files from the source node. Ensure snapshot files can be used during recovery by setting [indices.recovery.max_concurrent_snapshot_file_downloads] to be no greater than [25]

The `[25]` here is wrong, the 25 permits are shared across all inbound recoveries so we should divide the suggested value by `cluster.routing.allocation.node_concurrent_incoming_recoveries`. In extreme cases the user may have configured so many concurrent recoveries that the only reasonable limit is zero, and in that case we should suggest setting `indices.recovery.use_snapshots: false` instead.


server/src/main/java/org/elasticsearch/indices/recovery/RecoverySettings.java
return internalActionLongTimeout;
    }
    public ByteSizeValue getChunkSize() {
        return chunkSize;
    }
    public void setChunkSize(ByteSizeValue chunkSize) { 
        if (chunkSize.bytesAsInt() <= 0) {
            throw new IllegalArgumentException("chunkSize must be > 0");
        }
        this.chunkSize = chunkSize;
    }
    public void setRetryDelayStateSync(TimeValue retryDelayStateSync) {
        this.retryDelayStateSync = retryDelayStateSync;
    }
    public void setRetryDelayNetwork(TimeValue retryDelayNetwork) {
        this.retryDelayNetwork = retryDelayNetwork;
    }
    public void setActivityTimeout(TimeValue activityTimeout) {
        this.activityTimeout = activityTimeout;
    }
    public void setInternalActionTimeout(TimeValue internalActionTimeout) {
        this.internalActionTimeout = internalActionTimeout;
    }
    public void setInternalActionLongTimeout(TimeValue internalActionLongTimeout) {
        this.internalActionLongTimeout = internalActionLongTimeout;
    }
    public void setInternalActionRetryTimeout(TimeValue internalActionRetryTimeout) {
        this.internalActionRetryTimeout = internalActionRetryTimeout;
    }
    private void setMaxBytesPerSec(ByteSizeValue maxBytesPerSec) {