Added check for DHEater vulnerability and updated relevant tests (#211)

[BareqAZ]

Added a check for the DHEater vulnerability mentioned here: https://github.com/jtesta/ssh-audit/issues/211 And updated the tests. two things to note: Considering this issue is in the algorithm not the server, the vulnerability was documented in the algorithm itself rather than the CVEs section.

And I did have to edit the following docker test to expect a failure instead of a success: 749: run_openssh_test "8.0p1" "test3" "${PROGRAM_RETVAL_FAILURE}" I'm not sure if it's fine this way or if would you want to update the docker OpenSSH config instead. Either way, I thought I'd mention these here to be sure.