largefiles: add tests for summary/outgoing improved in subsequent patches
This patch adds tests for summary/outgoing improved in subsequent
patches, to reduce amount of diffs in each patches.
This patch adds new revisions below:
- revision #2 adds new largefiles, but they contain as same data as
one already existing
this causes that multiple standins refer the same data entity
- revision #3, #4 and #5 change the already existing largefile
this causes that multiple data entities are outgoing for the standin.
#5 can be used to check de-duplication of "(hash, filename)" pair.