[#54676742] dancarley/sneha Added mirror_rsynch user account and key to mirror boxes

Added a user mirror_rsynch on mirror boxes. This user is specifically
for mirrorer to push data to new mirror boxes.Using the accounts module
to do this.
[#54676742] dancarley/sneha changed target directory permission

gave access to mirror-rsync user
Tiny OCD changes
Merge pull request #8 from alphagov/54676742_push_data_to_mirrors

[#54676742] push data to mirrors
Merge branch 'master' of github.com:alphagov/govuk_mirror-puppet into better-ssl

Conflicts:
  hieradata/common.yaml