data validation BUGFIX checking when expression
data validation BUGFIX checking when expression

when statement was not validated in rpc, rpc-reply and notification,
which is required by RFC

PavolVican/libyang,PavolVican/libyang,PavolVican/libyang,PavolVican/libyang,lukasmacko/libyang,PavolVican/libyang,lukasmacko/libyang