Fix the tests so they don't fail with the recent updates

lib/logger.js

@@ -384,19 +384,35 @@ const flushAll = function(cb) {
     if (!cb || typeof cb !== 'function') {
         cb = debug;
     }
+
+    // Variables used to wait for all the flushes to be completed
+    let counter = 0;
+    const loggersCount = loggers.length;
+    const complete = (errors) => {
+        if (errors.length > 0) {
+            return cb(`The following errors happened while flushing all loggers: ${errors}`);
+        }
+        return cb();
+
+    };
+
     const errors = [];
     loggers.forEach((logger) => {
         logger._flush((err) => {
             if (err) {
                 errors.push(err);
             }
+            // Counter is incremented after each flush
+            if (++counter === loggersCount) {
+
+                /*
+                 * Flushed all the loggers
+                 * Completes by calling the callback
+                 */
+                complete(errors);
+            }
         });
     });
-
-    if (errors.length > 0) {
-        return cb(`The following errors happened while flushing all loggers: ${errors}`);
-    }
-    return cb();
 };
 
 exports.Logger = Logger;

test/logger.js

@@ -288,9 +288,6 @@ describe('Index meta', function() {
 });
 
 describe('Input validation', function() {
-    afterEach(function(done) {
-        Logger.flushAll(done);
-    });
     it('Sanity checks for Ingestion Key', function(done) {
         const bogusKeys = [
             'THIS KEY IS TOO LONG THIS KEY IS TOO LONG THIS KEY IS TOO LONG THIS KEY IS TOO LONG THIS KEY IS TOO LONG THIS KEY IS TOO LONG'