Pick the shortest available path suffix when generating skeleton path cover.

Pick the shortest available path suffix when generating skeleton path cover.

This also fixes a error in the generation process: sometimes in case
of loops the current node's suffix was set before all of its children
were processed.

Updated test results (in some cases .input files became larger because
of the above fix, in some cases they became smaller because we now pick
the shortest suffix).

Added new test; this one was found by slyfox's fuzzer and revealed the
above bug.