ovccclient-client: trigger place_pawn() when Idle
Like for adding tile, place a pawn when Idle (otherwise all actions are chained since signals are synchronous).
what's the rationale for this?
Found debug messages strangely ordered in the bot, dug a little and as I said in the commit message, this avoids geting signals chained synchronously in the middle of another handler. Also to keep handler short and just trigger actions for later run. Plus the fact that it's already the case few lines before for tile placement.