util/cedarish: Add mitigation for ImageMagick CVE-2016–3714
util/cedarish: Add mitigation for ImageMagick CVE-2016–3714

Upstream:
- heroku/stack-images@c9a1d5a59013d81c1239909a8fcefa369aa85a65
- heroku/stack-images@64fe8db09e76d0c3401fbbbbce01fb4da1b2f9d8

Signed-off-by: Jonathan Rudenberg <3692bfa45759a67d83aedf0045f6cb635a966abf@titanous.com>

flynn/flynn,lmars/flynn,flynn/flynn,lmars/flynn,flynn/flynn,lmars/flynn,lmars/flynn,flynn/flynn,philiplb/flynn,philiplb/flynn,philiplb/flynn,lmars/flynn,philiplb/flynn,philiplb/flynn,flynn/flynn