Fix bugs turned up by _GLIBCXX_DEBUG

Compiling with -D_GLIBCXX_DEBUG enables libstc++ "debug mode", where
additional debug information is tracked with iterators and reported if
iterators are misused. This turned up two bugs.

I threw in removing dead code and avoiding an unnecessary map lookup
while I was in the neighborhood.

fdbrpc/HealthMonitor.actor.cpp

@@ -29,10 +29,12 @@ void HealthMonitor::reportPeerClosed(const NetworkAddress& peerAddress) {
 }
 
 void HealthMonitor::purgeOutdatedHistory() {
-	for (auto it : peerClosedHistory) {
+	for (auto it = peerClosedHistory.begin(); it != peerClosedHistory.end();) {
-		if (it.first < now() - FLOW_KNOBS->HEALTH_MONITOR_CLIENT_REQUEST_INTERVAL_SECS) {
+		if (it->first < now() - FLOW_KNOBS->HEALTH_MONITOR_CLIENT_REQUEST_INTERVAL_SECS) {
-			peerClosedNum[it.second] -= 1;
+			auto& count = peerClosedNum[it->second];
-			ASSERT(peerClosedNum[it.second] >= 0);
+			--count;
+			ASSERT(count >= 0);
+			++it; // Increment before pop_front to avoid iterator invalidation
 			peerClosedHistory.pop_front();
 		} else {
 			break;

fdbserver/MoveKeys.actor.cpp

@@ -240,7 +240,6 @@ ACTOR Future<vector<vector<UID>>> additionalSources(Standalone<RangeResultRef> s
 
 	std::map<UID, StorageServerInterface> ssiMap;
 	for(int s=0; s<serverListValues.size(); s++) {
-		auto si = decodeServerListValue(serverListValues[s].get());
 		StorageServerInterface ssi = decodeServerListValue(serverListValues[s].get());
 		ssiMap[ssi.id()] = ssi;
 	}
@@ -260,7 +259,7 @@ ACTOR Future<vector<vector<UID>>> additionalSources(Standalone<RangeResultRef> s
 		}
 
 		for(int s=0; s<dest.size(); s++) {
-			if( std::find(src.begin(), src.end(), dest[s]) == dest.end() ) {
+			if (std::find(src.begin(), src.end(), dest[s]) == src.end()) {
 				destInterfs.push_back( ssiMap[dest[s]] );
 			}
 		}