Import image markdown for Github Enterprise Self-Managed
When working on !130688 (merged) , it was realized copying markdown attachments from GitHub Enterprise Self-Managed does not work.
Per: !130688 (comment 1547178663), importing GitHub Enterprise Self-Managed image markdown was never tested and should never have been working.
This is because the self-managed urls can be different depending on the object storage chosen. Eg. An example GCE URL would look like https://35.231.21.147/storage/user/4/files/a58ddef5-9601-4740-ad25-686a2e0da3f , which does not follow any url pattern matching we have implemented for scraping Github.
Note: This is different than GitHub's Enterprise SaaS offering, as that works the same as regular GitHub.com
Edited by Max Fan