Add read and execute permissions for galaxy-admins group

Add read end execute permissions on several galaxy directories for the galaxy-admins group:

• galaxy_config_dir: "{{ galaxy_root }}/config"
• galaxy_mutable_config_dir: "{{ galaxy_root }}/mutable-config"
• galaxy_mutable_data_dir: "{{ galaxy_root }}/mutable-data"
• galaxy_log_dir: "{{ galaxy_root }}/var/log/"