When cache pull fails on bst1 and is retried, it will also try to fetch sources

Noticed when trying to pull GCC (which is huge) from freedesktop-sdk remote CAS. Retry seems to not only trigger retry of cache pull but also fetch sources which seems unexpected.

Start by reproducing the cache-pull retry flow while pulling GCC from the freedesktop-sdk remote CAS. Trace whether retrying a failed cache pull also starts fetching sources, and use that observed behavior as the completion criterion; the report names no files or tests to begin with.

Written by the indexing model from the issue text.