Failed to start apache :
 * Starting web server apache2
 * 
 * The apache2 configtest failed.
Output of config test was:
[Sat May 16 01:48:35.669117 2015] [proxy_html:notice] [pid 2422] AH01425: I18n support in mod_proxy_html requires mod_xml2enc. Without it, non-ASCII characters in proxied pages are likely to display incorrectly.
AH00526: Syntax error on line 55 of /etc/apache2/apache2.conf:
Invalid command 'LockFile', perhaps misspelled or defined by a module not included in the server configuration
Action 'configtest' failed.
The Apache error log may have more information.