fix default value of php::fpm::pool::access_log_format

[lesinigo]

The default value for php::fpm::pool::access_log_format gets its escapes un-escaped by Puppet string management, resulting in a log line that looks like this:

127.0.0.1 -  04/Jul/2017:11:33:53 +0200GET /test.php404

this PR fixes the default value and gives you correctly formatted log lines like:

127.0.0.1 -  04/Jul/2017:12:36:24 +0200 "GET /test.php" 404

[bastelfreak]

oh annoying bug, thanks for the fix @lesinigo!