Update the hostname based on the prompt analysis.

def update_hostname(self, prompt):
        """Update the hostname based on the prompt analysis."""
        result = re.search(self.prompt_re, prompt)
        if result:
            hostname = result.group('hostname')
            self.log("Hostname detected: {}".format(hostname))
        else:
            hostname = self.device.hostname
            self.log("Hostname not set: {}".format(prompt))
        return hostname