Make tests pass with single-path symbolic execution [depends-on: #3969, blocks: #3976]

[tautschnig]

Each run of symbolic execution reports the number of properties that failed in
this run, and it isn't always possible to violate multiple properties along a
single path. All paths together, however, show the same property violations as
path-merging symbolic execution.

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[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: 44f92ad).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/98718450

[kroening]

Path-based should still be able to count the number of failed properties?
symex doesn't need these tweaks to the tests.

[tautschnig]

The question is when the output ** x of y failed (n iterations) should be printed. Maybe we should just print a summary at the end as well, just like VERIFICATION (FAILED|SUCCESSFUL) is also printed for the overall result?

[peterschrammel]

With #3969 the output will be the same as with multi-path symex, i.e. only the final collated results are reported.

[tautschnig]

Thanks @peterschrammel. I'll mark this one "depends-on: #3969" and will then close it as soon as that's merged.

[tautschnig]

Closing, just marked #3976 as depending on #3969.