minor update to work around concurrent modification exceptions occuring in the RemoveCondacts file in the computeIfAbsent method of Java maps.
minor update to work around concurrent modification exceptions occuring
in the RemoveCondacts file in the computeIfAbsent method of Java maps.

- we reimplement the computeIfAbsent method and omit the checks
- we are confident this is OK due to the fact that we are not changing
key -> value mappings during traversal.
andrewkatis/jkind-1,andrewkatis/jkind-1