mount helper region parameter should use VPC regions specifications like us-south not dal

[powellquiring]

See the docs:

https://github.com/IBM/vpc-file-storage-mount-helper

The available regions are dal, fra, lon, osa, sao, syd, tok, tor, wdc.

./install.sh region=dal

In vpc regions are us-south, eu-de, etc. Mixing classic names with VPC region names is not preferred. For backward compatibility it may be ok to keep dal but make an alias to us-south and correct all documentation. Do not feature the names like dal in the docs. The goal is to stop using those.

https://github.ibm.com/cloud-docs/overview/issues/583