Raise key length defaults

Extend RSA keylength to 2048 bits by default,
as the previous default of 1024 bit is considered
weak since 12/31/2010.

Also unify the message_md to the openssl builtin default.

Fixes bug 1103002

Change-Id: I70e90b7696f8a56073c3d6bdc9ed5d30cfa3401f
Merge "Raise key length defaults"