[misc] correcting SkySQL tests

Author: rusher

test/integration/test-pool-callback-event.js

@@ -9,6 +9,10 @@ const path = require('path');
 const os = require('os');
 
 describe('Pool callback event', () => {
+  before(function () {
+    if (process.env.SKYSQL != null) this.skip();
+  });
+
   it('pool connection creation', function (done) {
     this.timeout(10000);
     const pool = base.createPoolCallback();

test/integration/test-ssl.js

@@ -514,7 +514,7 @@ describe('ssl', function () {
   });
 
   it('Mutual authentication providing client keystore', function (done) {
-    if (process.env.SKYSQL) this.skip();
+    if (process.env.SKYSQL != null) this.skip();
     if (!sslEnable) this.skip();
     if (!ca || !clientKeystore) this.skip();
     if (!base.utf8Collation()) this.skip();