Tweak the config to use RDSEED or (fallback) RDRAND. Makes sure
we have initial random seed in cases where there is no other
random source if these are supported.
The default config in Alpine currently disables these, which makes
it pretty useless, as there is no motherboard rng support any more.
Replaces #517Fix#514Fix#183
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
