Left-trim whitespace from IRC messages

Change I270bde418 delegated UDP RC logging to wfErrorLog() in the interest of
having a single reference UDP emitter in core. wfErrorLog()'s behavior is
compatible with RecentChange::sendToUDP in all respects except one, which we
missed: the former adds an extra space between the prefix and the message,
whereas the latter does not. This introduced a leading space to IRC messages,
which broke some regexes. The easiest and simplest way of fixing it is to trim
the leading whitespace in the IRC echo script.

Change-Id: Ia027f7c6f9ccb8dcf6983bab66d4a4afadc25a37