Fix QEMU feature checks during startup #2919

Job	Run time
Code (oldstable)	7m 23s
Code (stable)	7m 28s
Client (oldstable, ubuntu-latest)	59s
Code (tip)	10m 46s
Client (oldstable, macos-latest)	1m 2s
Client (oldstable, windows-latest)	2m 55s
Client (stable, ubuntu-latest)	1m 8s
System (stable, cluster, dir)	13m 18s
Client (stable, macos-latest)	1m 14s
System (stable, cluster, btrfs)	13m 13s
Client (stable, windows-latest)	1m 39s
System (stable, cluster, lvm)	13m 23s
System (stable, cluster, zfs)	12m 42s
System (stable, cluster, ceph)	18m 13s
System (stable, cluster, random)	13m 50s
Documentation	5m 6s
System (stable, standalone, dir)	22m 4s
System (stable, standalone, btrfs)	23m 50s
System (stable, standalone, lvm)	39m 35s
System (stable, standalone, zfs)	38m 25s
System (stable, standalone, ceph)	1h 15m 14s
System (stable, standalone, random)	35m 0s
System (oldstable, cluster, dir)	12m 20s
System (oldstable, standalone, dir)	22m 14s
System (tip, cluster, dir)	14m 26s
System (tip, standalone, dir)	24m 53s
	7h 12m 20s

Provide feedback