The variable VersionInfo is supposed to be set by `go build -X ...` during link time but should not be modified at runtime.
This change ensures the underlying var is private and can only be accessed by a public getter.
In the light of extending our eKMS support it will be helpful
to have a tighter use of the word "KMS".
KMS should refer to the actual component that manages keys.
The keyservice, also called KMS in the constellation code,
does not manage keys itself. It talks to a KMS backend,
which in turn does the actual key management.
