Cache elasticsearch downloads using dotfile

What does this Merge Request do and why?

This MR fixes a bug introduced in !1937 (merged) where elasticsearch*.tar.gz files were removed (a good thing) but inadvertently resulted in elasticsearch-7.10.2.tar.gz being downloaded again each and every time a gdk reconfigure/update was issued.

Merge Request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise Issue to follow-up.
• Documentation added/updated, if needed.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.

Closes #1229 (closed)