Make PHP FPM pool configurable

defaults/main.yml

@@ -53,6 +53,13 @@ php_short_open_tag: 'Off'
 php_upload_max_filesize: '2M'
 php_zend_assertions: '-1'
 
+# PHP FPM
+php_fpm_max_children: '10'
+php_fpm_start_servers: '4'
+php_fpm_min_spare_servers: '2'
+php_fpm_max_spare_servers: '6'
+php_fpm_max_requests: '2000'
+
 # apc.ini
 apc_rfc1867: '1'
 apc_shm_size: '256M'