This commit enforces the usage of AES-256
for config and IAM data en/decryption in FIPS
mode.
Further, it improves the implementation of
`fips.Enabled` by making it a compile time
constant. Now, the compiler is able to evaluate
the any `if fips.Enabled { ... }` at compile time
and eliminate unused code.
Signed-off-by: Andreas Auernhammer <aead@mail.de>