Switch these tests to use the same certificate as used by the other tests.

They failed for the same reason - 512 bit RSA key is too small for new kinds of TLS.


git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/branches/failing-tls-tests-7370@43110 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb