* Fix cubbyhole and revocation for legacy service tokens
Legacy service tokens generated in Vault 1.10+ with env var
VAULT_DISABLE_SERVER_SIDE_CONSISTENT_TOKENS=true are not assigned
a cubbyhole ID. The implication is that cubbyhole/ cannot be
used, nor can the tokens be revoked.
This commit assigns a cubbyhole ID to these tokens and adds
a new test case to see that cubbyhole and revocation works correctly.
* add changelog
* add godoc to test cases