enh: allow user to reboot from inside the VM (#790)

JIRA: ALEPH-472

Important note: Previously --no-reboot was used so if the BIOS failed to boot the VM because of for example an invalid disk image provided by the user
then the QEMU process and the controller would halt.
The new behaviour is that the VM will reboot indefinetly. But it should be catched by the wait for init procedure that will test by ping.

This new modification was necessary because the GPU VM need a reboot for their setup.
And generaly user would be confused when rebooted VM would not restart.

The --no-reboot flag was kept for ConfidentialVM as confidential VM do not support reboot anyway

Author: olethanh

src/aleph/vm/hypervisors/qemu/qemuvm.py

@@ -93,7 +93,8 @@ async def start(
             # To debug you can pass gtk or curses instead
             "-display",
             "none",
-            "--no-reboot",  # Rebooting from inside the VM shuts down the machine
+            # "--no-reboot",  # Rebooting from inside the VM shuts down the machine
+            # Disable --no-reboot so user can reboot from inside the VM. see ALEPH-472
             # Listen for commands on this socket
             "-monitor",
             f"unix:{self.monitor_socket_path},server,nowait",