[BUGFIX] Install the missing xml module for PHP

recipes/default.rb

@@ -48,7 +48,7 @@ include_recipe 'apache2::mod_ssl'
 
 if node['platform_version'] == '16.04'
 	package 'libapache2-mod-php7.0'
-	%w(php php-cli php-curl php-intl php-gd php-mcrypt php-mysql ).each do |name|
+	%w(php php-cli php-curl php-intl php-gd php-mcrypt php-mysql php-xml).each do |name|
 		package name do
 			action :install
 		end