Item12027: Hard code LogDispatchContrib to utf8

Log::Dispatch sets the file encoding when the logger is instantiated. So
we can't switch on the fly to utf8 encoding when the log record requires
it.

git-svn-id: http://svn.foswiki.org/trunk/LogDispatchContrib@17220 0b4bb1d4-4e5a-0410-9cc4-b2b747904278