Suspend the GNS3 VM.

def suspend(self):
        """
        Suspend the GNS3 VM.
        """

        if self._vmx_path is None:
            raise GNS3VMError("No VMX path configured, can't suspend the VM")
        try:
            yield from self._execute("suspend", [self._vmx_path])
        except GNS3VMError as e:
            log.warning("Error when suspending the VM: {}".format(str(e)))
        log.info("GNS3 VM has been suspended")
        self.running = False