The rstr library relies on the normal random.SystemRandom() and does not
perform additional functionalites that would require a whole dependency
to be added to pegleg. This patch set places in the logic into pegleg's
crypto generation rather than using the whole rstr library.
Change-Id: I20c0ceae8ac7d11468f325cd6a4cc035fc176b14
Signed-off-by: Tin Lam <tin@irrational.io>