Qubes 4.0 qvm-run should be asynchronous by default like in 3.2

[qubesuser]

Qubes OS version:

R4.0-rc2

Steps to reproduce the behavior:

1. Use qvm-run to start something

Expected behavior:

qvm-run exits immediately (unless --pass-io is specified)

Actual behavior:

qvm-run waits for the program to terminate

General notes:

Qubes 3.2 behaved like this (unless I'm crazy), and I think compatibility should be kept.

A --wait flag should be introduced to wait for the program instead of making it the default.

Also there should ideally be --startup-notification flag that waits for startup notification and relays it to dom0 so the desktop GUI hourglass cursor works properly.