process kill with --no-wait not returns control to user in new asyncio daemon

[unkcpz]

Think this is duplicate of #4649 but with a more clear root of the issue.

[How to reproduce]:
After submitting a calculation to the daemon and when it starts to transport data to the remote cluster, kill the process with verdi process kill <pk>. It is expected to give the cmdline control back to the user since --no-wait option is the default one. However, in new asyncio daemon it is 'wait' until the transports over the connection are cancelled (I'm not sure what's really happened here when we kill a process).

In a word, the process kill with --no-wait behave like option wait and that is not we want.