nomodule attribute is not respected on scripts with sources

[mgol]

Description

PR #3869 added support for <script type="module"> & some support for the nomodule attribute but with no tests for nomodule and with the attribute only respected on inline scripts.

Ref #3871

Link to test case

http://plnkr.co/edit/rZJmEFJIpPOHDMNJUdxz?p=preview

In modern browsers you should see PASS, instead you'll see FAIL: 2, indicating 2 out of 4 scripts get executed; those are the src-based scripts.

[mgol]

PR: #4282