Instead of creating a redeemScript with CreateMultisigRedeemscript and
then getting the destination with AddAndGetDestinationForScript, do
both in the same function.
CreateMultisigRedeemscript is changed to AddAndGetMultisigDestination.
It creates the redeemScript and returns it via an output parameter. Then
it calls AddAndGetDestinationForScript to add the destination to the
keystore and get the proper destination.
This allows us to inspect the public keys in the redeemScript before creating
the destination so that the correct destination is used when uncompressed
pubkeys are in the multisig.
