[token-server] Update directory structure to use one volume

Summary: Server throws errors when attempt to delete icons. Doing some digging, looks like moving files between volumes is an issue. So, use one volume.

Test Plan: Build with all secrets and deploy in docker, create a token, ban the icon. Or, deploy and see how server behaves.

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D15749