MEDIUM: ssl: fix detection of ephemeral diffie-hellman key exchange by using the cipher description.

In OpenSSL, the name of a cipher using ephemeral diffie-hellman for key
 exchange can start with EDH, but also DHE, EXP-EDH or EXP1024-DHE.
We work around this issue by using the cipher's description instead of
the cipher's name.
Hopefully the description is less likely to change in the future.