Eliminate one reason for non-determinism of predicate abstraction:
we collected all new predicates in a ListMultimap
and iterated over the keys, but the Multimap is normally based on a
HashMap.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14819 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c