Load data erroneously requires cache directory to exist.

[grosscol]

Describe the bug
CLI commands to load data fail if CRAM cache path does not exist.

To Reproduce
Steps to reproduce the behavior:

1. Run

   api/venv/bin/flask load-genes canonical_transcripts.tsv.gz \
     omim_ensembl_refs.tsv.gz \
     hgcn_genenames.tsv.gz \
     gencode.v38.annotation.gtf.gz

2. Wait for execution to halt with error Exception: Provided CRAM cache path does not exist.

Expected behavior
Gene collections to be loaded into mongo db from given inputs.

Desktop (please complete the following information):

Distributor ID: Ubuntu
Description:    Ubuntu 20.04.5 LTS
Release:        20.04
Codename:       focal

Additional context
Loading backing data post data_prep processing.