Merge inconsistent-hash-7651: fix test_inspectCertificate

Author: glyph

Reviewer: mithrandi

Fixes: #7651

twisted.internet.ssl.Certificate(...).getPublicKey().keyHash() now produces a
stable value regardless of OpenSSL version.  Unfortunately this means that it
is different than the value produced by older Twisted versions.

git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/trunk@43179 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb