Fix linting errors in query middleware

Signed-off-by: João Victor Tozatti Risso <jvtr12@inf.ufpr.br>

src/libs/middlewares/query.js

-const libs = process.cwd() + '/libs/';
-const log = require(libs + 'log')(module);
-const execQuery = require(libs + 'db/query_exec');
+const libs = `${process.cwd()}/libs`;
+const log = require(`${libs}/log`)(module);
+const execQuery = require(`${libs}/db/query_exec`);
 
 function query(req, res, next) {
-    log.debug(req.query)
+    log.debug(req.query);
     execQuery(req.query.text, req.query.values).then((result) => {
         log.debug(result);
         req.result = result;