CheckTx doesn't verify message routing

[alexanderbez]

Summary of Bug

// CheckTx implements the ABCI interface. It runs the "basic checks" to see
// whether or not a transaction can possibly be executed, first decoding, then
// the ante handler (which checks signatures/fees/ValidateBasic), then finally
// the route match to see whether a handler exists.
//
// NOTE:CheckTx does not run the actual Msg handler function(s).

Currently CheckTx does all of what is stated in its godoc except for verifying a router exists for each message! This isn't a big deal or exploitable, but should be fixed nonetheless. I believe we can do this by simply remove the following from BaseApp#runTx:

	if mode == runTxModeCheck {
		return result
	}

This is because BaseApp#runMsgs already has this check and doesn't execute the matched message handler during CheckTx.

Caught by @gamarin2

Version

b2f8c58

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[rdrahul]

@alexanderbez I want to take this up.

[alexanderbez]

Yes please @rdrahul, that would be helpful!