Fix find --json to output json once more.

Reversion from commit 436f10771, CustomOutput was forcing quiet output
which overrode the json setting.

find happened to be the only command that uses CustomOutput and also
outputs json. (metadata --get does also use CustomOutput and --json does not
enable json output for that, which may be an oversight, but was already the
behavior before this regression.)

Messages.hs

@@ -99,7 +99,10 @@ showStartMessage (StartUsualMessages command ai) = do
 		_ -> noop
 	showStartMessage (StartMessage command ai)
 showStartMessage (StartNoMessage _) = noop
-showStartMessage (CustomOutput _) = Annex.setOutput QuietOutput
+showStartMessage (CustomOutput _) =
+	outputType <$> Annex.getState Annex.output >>= \case
+		NormalOutput -> Annex.setOutput QuietOutput
+		_ -> noop
 
 -- Only show end result if the StartMessage is one that gets displayed.
 showEndMessage :: StartMessage -> Bool -> Annex ()