test: changing process.exit to return while skipping tests

This patch uses `return` statement to skip the test instead of using
`process.exit` call.

PR-URL: https://github.com/nodejs/io.js/pull/2109
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>

test/parallel/test-http-url.parse-https.request.js

@@ -4,7 +4,7 @@ var assert = require('assert');
 
 if (!common.hasCrypto) {
   console.log('1..0 # Skipped: missing crypto');
-  process.exit();
+  return;
 }
 var https = require('https');