if the last state in the reached set is a target state, then assume this is the only target (non-global refinement)

this distinction is needed, because multiple targets can occur during global refinement, but also when the analysis continues after having found valid targets (c.f. analysis.stopAfterError=false), and without this change, the valid target was interpreted as a repeated counterexample



git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14851 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c