Include X-Request-ID header in apache logs

[SamuAlfageme]

By extending current LogFormat to include \"%{X-Request-ID}i\" - ref. http://httpd.apache.org/docs/current/mod/mod_log_config.html#formats

X-Request-ID in ownCloud:

• Use X-Request-ID header as request id if provided by client owncloud/core#28144
• Client implementation: Send a unique X-Request-ID header to allow tracing requests in apache and owncloud logs. owncloud/client#5853 and Account: Send a X-Request-ID header #5853 owncloud/client#5897

[tboerger]

This is possible now, just add the environment variable APACHE_LOG_FORMAT with value requestid and you will have the log format %h %l %u %t "%r" %>s %O "%{Referer}i" "%{User-Agent}i" "%{X-Request-ID}i"