Drop verbose log entries in BP when no network graph is provided

[TheBlueMatt]

If no network graph is provided to the BackgroundProcessor, we log every time the processor loop goes around (at least every 100ms, if not more) which fille up logs with useless indications that we have no network graph.

[TheBlueMatt]

Oops, there was a test that was relying on these logs:

$ git diff-tree -U1 969613df f6cd2f4b
diff --git a/lightning-background-processor/src/lib.rs b/lightning-background-processor/src/lib.rs
index 4201fc9ed..8aae70395 100644
--- a/lightning-background-processor/src/lib.rs
+++ b/lightning-background-processor/src/lib.rs
@@ -1072,6 +1072,7 @@ mod tests {
 			let log_entries = nodes[0].logger.lines.lock().unwrap();
-			let expected_log_a = "Assessing prunability of network graph".to_string();
-			let expected_log_b = "Not pruning network graph, either due to pending rapid gossip sync or absence of a prunable graph.".to_string();
-			if log_entries.get(&("lightning_background_processor".to_string(), expected_log_a)).is_some() &&
-				log_entries.get(&("lightning_background_processor".to_string(), expected_log_b)).is_some() {
+			let loop_counter = "Calling ChannelManager's timer_tick_occurred".to_string();
+			if log_entries
+				.get(&("lightning_background_processor".to_string(), loop_counter)).unwrap_or(0) > 1
+			{
+				// Wait until the loop has gone around at least twice.
 				break
$

[TheBlueMatt]

Oops, the one time rustc doesn't add the neccessary references to make it compile...

$ git diff-tree -U1 f6cd2f4b 46333aff
diff --git a/lightning-background-processor/src/lib.rs b/lightning-background-processor/src/lib.rs
index 8aae70395..4970c6920 100644
--- a/lightning-background-processor/src/lib.rs
+++ b/lightning-background-processor/src/lib.rs
@@ -1073,4 +1073,4 @@ mod tests {
 			let loop_counter = "Calling ChannelManager's timer_tick_occurred".to_string();
-			if log_entries
-				.get(&("lightning_background_processor".to_string(), loop_counter)).unwrap_or(0) > 1
+			if *log_entries.get(&("lightning_background_processor".to_string(), loop_counter))
+				.unwrap_or(&0) > 1
 			{