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.


test/framework/src/main/java/org/elasticsearch/test/MockLogAppender.java
protected final String name;
        protected final String logger;
        protected final Level level;
        protected final Pattern pattern;
        volatile boolean saw;
        public PatternSeenEventExpectation(String name, String logger, Level level, String pattern) {
            this.name = name;
            this.logger = logger;
            this.level = level;
            this.pattern = Pattern.compile(pattern);
        }
        @Override
        public void match(LogEvent event) {
            if (event.getLevel().equals(level) && event.getLoggerName().equals(logger)) {
                if (pattern.matcher(event.getMessage().getFormattedMessage()).matches()) {
                    saw = true;
                }
            }
        }
        @Override
        public void assertMatched() {
            assertThat(name, saw, equalTo(true));
        }
    }
    /**
     * A wrapper around {@link LoggingExpectation} to detect if the assertMatched method has been called
     */
    private static class WrappedLoggingExpectation implements LoggingExpectation {