fix(prometheus): Set permissions on /prometheus

[jsirianni]

Description of Changes

On GKE we get permission issues. Minikube works either way. The user id 65534 is what the prometheus process runs as, and maps to the nobody user.

/prometheus $ ls -la /prometheus/
total 20
drwxrwxrwx    4 nobody   nobody        4096 Dec  6 17:00 .
drwxr-xr-x    1 root     root          4096 Dec  6 17:00 ..
drwxr-xr-x    2 nobody   nobody        4096 Dec  6 16:57 chunks_head
-rw-r--r--    1 nobody   nobody           0 Dec  6 17:00 lock
-rw-r--r--    1 nobody   nobody       20001 Dec  6 17:00 queries.active
drwxr-xr-x    2 nobody   nobody        4096 Dec  6 17:00 wal

Please check that the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• CI passes