Fixes a deadlock in the background scanner that occurs on single-core
Linux devices. This happens because the background scanner would `block`
on a background thread waiting for a future, but on single-core Linux
devices there would be no other thread to pick it up. This mostly
affects SSH remoting use cases where it's common for servers to have 1
vCPU.

Closes #43884 
Closes #43809

Release Notes:

- Fix SSH remoting hang when connecting to 1 vCPU servers