This is in anticipation of #1110, which only exhibits inside a with_items:
loop. For this refactor `loop:` is used, to confirm the refactored tests are
still correct. A subsequent commit will change them to with_items.
The content of the files and their SHA1 checksums are unchanged.
Reverts 49736b3a, large file copies can't avoid the RTT.
The parent stack must be blocked while FileService progresses, as unlike
the small file path, it does not make a snapshot of the (possibly
temporary) file passed by the action plug-in. So we need to keep that
file alive while the service runs.
Add a new integration test and a new soak test to cover both.
Alex Willmer