tpchgen docker syntax change prevents volume from binding

[avantgardnerio]

Describe the bug
PR #2741 appears to have introduced a bug in this line. Because the imagename:version is included before the -v the rest of the line is interpreted as arguments to the container, instead of arguments to docker, so the volume is not mounted, and the output is lost.

To Reproduce

1. cd benchmarks && rm -rf data/
2. ./tpch-gen.sh 0.1
3. ls -l data/
4. Observe no files

Expected behavior
.tbl files have been copied into the volume on the host machine.