collectd: fix memory stat collection configuration

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/memory.html#usage-in-bytes says
this is the most efficient approach for v1. It says RSS+CACHE(+SWAP) is the more accurate value.
Elsewhere in the note in https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v1/memory.html#stat-file,
it says "‘rss + mapped_file” will give you resident set size of cgroup." Overall, it's not clear how
to compute the values so we just use the file.

https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html is better. https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html#memory
says the values are separated out.

src/routes/graphs.js

@@ -7,11 +7,11 @@ exports = module.exports = {
 
 const assert = require('assert'),
     graphs = require('../graphs.js'),
-    safe = require('safetydance'),
-    middleware = require('../middleware/index.js'),
-    url = require('url'),
     HttpError = require('connect-lastmile').HttpError,
-    HttpSuccess = require('connect-lastmile').HttpSuccess;
+    HttpSuccess = require('connect-lastmile').HttpSuccess,
+    middleware = require('../middleware/index.js'),
+    safe = require('safetydance'),
+    url = require('url');
 
 // for testing locally: curl 'http://127.0.0.1:8417/graphite-web/render?format=json&from=-1min&target=absolute(collectd.localhost.du-docker.capacity-usage)'
 // the datapoint is (value, timestamp) https://buildmedia.readthedocs.org/media/pdf/graphite/0.9.16/graphite.pdf
@@ -46,7 +46,7 @@ async function getAppGraphs(req, res, next) {
 
     if (!req.query.fromMinutes || !parseInt(req.query.fromMinutes)) return next(new HttpError(400, 'fromMinutes must be a number'));
 
-    const fromMinutes = parseInt(req.query.fromMinutes) || 60;
+    const fromMinutes = parseInt(req.query.fromMinutes);
     const noNullPoints = !!req.query.noNullPoints;
     const [error, result] = await safe(graphs.getByAppId(req.app.id, fromMinutes, noNullPoints));
     if (error) return next(new HttpError(500, error));