Change hash and keysize defaults to modern standards

Change keysize defaults from 1024 to 2048 bits and change the default
hash from md5 to sha256.  Also, removed an oddly-specific call for sha1
in one instance.

Signed-off-by: Josh Cepek <josh.cepek@usa.net>
Signed-off-by: Eric F Crist <ecrist@secure-computing.net>