Fix typo, change virtio-rng default to urandom

# gpg: Signature made Wed 03 Jul 2019 16:24:53 BST
# gpg:                using RSA key CD2F75DDC8E3A4DC2E4F5173F30C38BD3F2FBE3C
# gpg:                issuer "laurent@vivier.eu"
# gpg: Good signature from "Laurent Vivier <lvivier@redhat.com>" [full]
# gpg:                 aka "Laurent Vivier <laurent@vivier.eu>" [full]
# gpg:                 aka "Laurent Vivier (Red Hat) <lvivier@redhat.com>" [full]
# Primary key fingerprint: CD2F 75DD C8E3 A4DC 2E4F  5173 F30C 38BD 3F2F BE3C

* remotes/vivier2/tags/trivial-branch-pull-request:
  docs/devel/testing: Fix typo in dockerfile path
  VirtIO-RNG: Update default entropy source to `/dev/urandom`
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>