roles/php-fpm: Updates for Debian 9 (stretch)

Debian 9 is still in beta and doesn't have nginx.org builds yet, so
we need to use the nginx package in Debian's repositories, and that
required a bit of a different configuration.

After official nginx.org builds are released we can revert this.

roles/php-fpm/templates/php7.0-pool.conf.j2

@@ -22,8 +22,13 @@
 ; Unix user/group of processes
 ; Note: The user is mandatory. If the group is not set, the default user's group
 ;       will be used.
+{% if ansible_distribution == 'Debian' and ansible_distribution_major_version | version_compare('9', '==') %}
+user = www-data
+group = www-data
+{% else %}
 user = nginx
 group = nginx
+{% endif %}
 
 ; The address on which to accept FastCGI requests.
 ; Valid syntaxes are:
@@ -44,8 +49,13 @@ listen = /run/php/php7.0-fpm-{{ domain_name }}.sock
 ; BSD-derived systems allow connections regardless of permissions.
 ; Default Values: user and group are set as the running user
 ;                 mode is set to 0660
+{% if ansible_distribution == 'Debian' and ansible_distribution_major_version | version_compare('9', '==') %}
+listen.owner = www-data
+listen.group = www-data
+{% else %}
 listen.owner = nginx
 listen.group = nginx
+{% endif %}
 ;listen.mode = 0660
 ; When POSIX Access Control Lists are supported you can set them using
 ; these options, value is a comma separated list of user/group names.