Remove caching of tasks, faults and operations

No longer seems to provide significant performance benefit to justify the
drawback of the added code complexity and the additional DB write query.

lib/nbi.ts

@@ -261,13 +261,11 @@ async function handler(
       if (channel.startsWith("task_")) {
         const objId = new ObjectId(channel.slice(5));
         await collections.tasks.deleteOne({ _id: objId });
-        await cache.del(`${deviceId}_tasks_faults_operations`);
         response.writeHead(200);
         response.end();
         return;
       }
 
-      await cache.del(`${deviceId}_tasks_faults_operations`);
       response.writeHead(200);
       response.end();
     } else {
@@ -312,7 +310,6 @@ async function handler(
           deviceId,
           30000
         );
-        await cache.del(`${deviceId}_tasks_faults_operations`);
         if (url.searchParams.has("connection_request")) {
           if (socketTimeout) request.socket.setTimeout(socketTimeout);
           response.writeHead(202, {
@@ -456,7 +453,6 @@ async function handler(
           _id: `${deviceId}:task_${taskId}`,
         });
 
-        await cache.del(`${deviceId}_tasks_faults_operations`);
         response.writeHead(200);
         response.end();
       } else {
@@ -475,7 +471,6 @@ async function handler(
           _id: `${deviceId}:task_${taskId}`,
         });
 
-        await cache.del(`${deviceId}_tasks_faults_operations`);
         response.writeHead(200);
         response.end();
       } else {