i=grev
i=adilger
branch=b1_6

change rundbench script to use contents of DBENCH_LIB variable to
find the location of the dbench executable (like acceptance-small.sh does)
so that we use the same environment variables to specify the location
of the dbench executable in both acceptance-small.sh and rundbench
instead of using different environment variables to configure the
same thing in the two different scripts.