Date picker date format incorrect when server language is not English

Jira should always default to english if an existing locale cannot be found. This will avoid problems like in JRA-8667, where jira is using the Ukrainian locale that is not supported. The 'None' option should also be removed in the Default Locale in General Configurations.

However jira should still default to system when jira is in setup. The only difference is that if no language pack is found then English is chosen instead of 'None'.