SSH key pairs deployed via the user's ssh_keys_pillar dict aren't
handled the same as the user's ssh_keys, e.g., file ownership and
permissions aren't specified, and the keying material gets copied
directly into the SLS file.  This change rewrites the two templated
file.managed states to behave as follows:

  - set the files' owner to be the user

  - set the files' group to be the user's primary group

  - for the public key, set the mode to 644 (u=rw,go=r)

  - for the private key, set the mode to 600 (u=rw,g=)

  - pull the files' contents directly from pillar