common/archive: Handle single slash after protocol in lookup_origin
Some external resolver or software might mangle the "://" character sequence into ":/" for the origin qualifier value of a SWHID.
This can lead to 404 errors when trying to resolve such a SWHID as the origin will be found missing due to the typo.
So handle that special case to avoid such errors.
Related to T2797
Closes #2878 (closed)
Migrated from D4729 (view on Phabricator)