Fixing a number of scaling issues:

- Missed closing of file descriptor made ForkingTaskExecutor
  silently die after running out of FDs
- Tightened up scope for locks to prevent http timeout
- Simplified threadpool

daggyr/libdaggyr/src/Server.cpp

@@ -161,8 +161,6 @@ namespace daggy::daggyr {
                      .resourcesUsed = resourcesUsed});
     }
 
-    std::cout << "Enqueuing " << runID << " / " << taskName << std::endl;
-
     response.send(Pistache::Http::Code::Ok, "");
   }
 
@@ -202,8 +200,6 @@ namespace daggy::daggyr {
           curCapacity_.cores += it->resourcesUsed.cores;
           curCapacity_.memoryMB += it->resourcesUsed.memoryMB;
         }
-        std::cout << "Resolved " << it->runID << " / " << it->taskName
-                  << std::endl;
         it = pending_.erase(it);
       }
       else {