cooker/knotty: Prefix parse logs with filename being parsed

cooker/knotty: Prefix parse logs with filename being parsed

We now prefix log messages coming from worker task context with the
PF and task info, however parsing messages all have to be manually
prefixed which is ugly and error prone. This change modifies the log
handler filter so this happens automatically, meaning we don't have
to change every message to include that information. This makes error
messages longer but more usable.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>