Fix ssh_auth.present test when enc != ssh-rsa

When using fullkeys, test=True will fail if the key encryption is not ssh-rsa.

For the following example (in salt documentation):

sshkeys:
  ssh_auth:
    - present
    - user: root
    - enc: ssh-rsa
    - options:
      - option1="value1"
      - option2="value2 flag2"
    - comment: myuser
    - names:
      - AAAAB3NzaC1kc3MAAACBAL0sQ9fJ5bYTEyY==
      - ssh-dss AAAAB3NzaCL0sQ9fJ5bYTEyY== user@domain
      - option3="value3" ssh-dss AAAAB3NzaC1kcQ9J5bYTEyY== other@testdomain
      - AAAAB3NzaC1kcQ9fJFF435bYTEyY== newcomment

ssh-dss AAAAB3NzaCL0sQ9fJ5bYTEyY== user@domain will be tested against ssh-rsa and not ssh-dss.

This commit fixes the problem.