Reenable samtools read count cross checks in HtsjdkReadsRddTest.testReadIntervals

[cmnbroad]

HtsjdkReadsRddTest.testReadIntervals cross checks its output by verifying that the read counts as returned by htsjdk and samtools are the same. Samtools/htslib have a bug (samtools/htslib#1387) that can return incorrect read counts for unmapped reads, so this checking is disabled by #164. When a version of samtools with a fix for that issue is released, we should upgrade disq to use the new version and reenable the cross checks.