set default to BOTTOM (instead of TOP) for option cpa.value.refinement.restart, this resembles more the way it worked before (i.e., lazy-abstraction, where lower parts of ARG are refined, instead restarting at root node [c.f. cpa.value.refinement.restart=TOP])

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14564 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c