Workaround for thumbnail pre rendering with PHP < 5.4.7

Since this code is dealing with scheme-less URLs, parse_url()
can cause issues in older versions of PHP.

Change-Id: Ic1276feed9ed51772a05c4a73c787a315b848066
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/301
Merge "Workaround for thumbnail pre rendering with PHP < 5.4.7"