Improvements to munge_chr_id subroutine in HTSAdaptor

Created by: rishidev

Various improvements to the munge_chr_id subroutine in HTSAdaptor, which were causing a crash on web when zooming in to view BAM/CRAM files.

1. changed the call to get a file handle directly from Bio::DB::HTS directly instead of re-using the call to the HTSAdaptors own htsfile open
2. We don't need the 1:1 in the region specifier with HTSlib
3. calls to $htsfile->close() ; before returning a value
4. removed unused ret_id variable