snp_filter: Do not skip SNP filter workload
snp_filter: Do not skip SNP filter workload

To avoid skewing benchmark results down, reinstate the SNP filter and
add a loop to revert the effects of applying the filter.

NVlabs/firepony,broadinstitute/firepony,NVlabs/firepony,broadinstitute/firepony,NVlabs/firepony,NVlabs/firepony,broadinstitute/firepony,broadinstitute/firepony