silence log messages from htslib
silence log messages from htslib

This prevents spurious error messages due to missing (but unneeded )
idx files. This commit disables all htslib logs and may have to be
be localized to just pysam.AlignmentFile() initializations.

MikkelSchubert/paleomix,MikkelSchubert/paleomix,MikkelSchubert/paleomix