get root user password.

def _get_root(self):
        """get root user password."""
        _DEFAULT_USER_DETAILS = {"level": 20, "password": "", "sshkeys": []}
        root = {}
        root_table = junos_views.junos_root_table(self.device)
        root_table.get()
        root_items = root_table.items()
        for user_entry in root_items:
            username = "root"
            user_details = _DEFAULT_USER_DETAILS.copy()
            user_details.update({d[0]: d[1] for d in user_entry[1] if d[1]})
            user_details = {
                key: py23_compat.text_type(user_details[key])
                for key in user_details.keys()
            }
            user_details["level"] = int(user_details["level"])
            user_details["sshkeys"] = [
                user_details.pop(key)
                for key in ["ssh_rsa", "ssh_dsa", "ssh_ecdsa"]
                if user_details.get(key, "")
            ]
            root[username] = user_details
        return root