Check if a username/password combination is valid.

def check_auth(self, username, password):
        """Check if a username/password combination is valid."""
        if username == self.args.username:
            from glances.password import GlancesPassword
            pwd = GlancesPassword()
            return pwd.check_password(self.args.password, pwd.sha256_hash(password))
        else:
            return False