manage unitig concurrency

Link: https://github.com/GeneAssembly/biosal/issues/651
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
unitig: the highest name wins if both have an identical length

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
unitig: the number of unitig vertices is deterministic

[boisvert@bigmem biosal]$ sha1sum run-1 run-2
06622cb9e6d8479b2bdd81c62d793e979d62ce2c  run-1
06622cb9e6d8479b2bdd81c62d793e979d62ce2c  run-2

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
the number of \"DEBUG current_has_duplicate\" and \"already visited\" lines must match

Link: https://github.com/GeneAssembly/biosal/issues/681
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
unitig: add starting kmer in visited list

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
fix white spaces

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>