Rationale: The HAVEGE random generator has too many caveats to be a
standard generator that people rely on. The HAVEGE random generator is not
suitable for virtualized environments. In addition the HAVEGE random
generator is dependent on timing and specific processor traits that
cannot be guaranteed by default on compile time.

Our advice: only use HAVEGE as an additional random source for your
entropy pool, never as your primary source.
(cherry picked from commit 08f06cf4)