incusd/instance/qemu: Don't fail on console retrival issue #2821

Job	Run time
Documentation	6m 19s
Client (oldstable, ubuntu-latest)	1m 5s
Code (oldstable)	7m 33s
Client (oldstable, macos-latest)	1m 19s
Code (stable)	7m 29s
Client (oldstable, windows-latest)	2m 1s
Code (tip)	10m 22s
Client (stable, ubuntu-latest)	1m 13s
System (stable, cluster, dir)	13m 44s
System (stable, cluster, btrfs)	12m 9s
Client (stable, macos-latest)	1m 3s
Client (stable, windows-latest)	1m 36s
System (stable, cluster, lvm)	13m 56s
System (stable, cluster, zfs)	13m 46s
System (stable, cluster, ceph)	17m 27s
System (stable, cluster, random)	14m 34s
System (stable, standalone, dir)	23m 49s
System (stable, standalone, btrfs)	22m 56s
System (stable, standalone, lvm)	41m 7s
System (stable, standalone, zfs)	37m 59s
System (stable, standalone, ceph)	1h 15m 17s
System (stable, standalone, random)	22m 54s
System (oldstable, cluster, dir)	11m 57s
System (oldstable, standalone, dir)	22m 1s
System (tip, cluster, dir)	14m 55s
System (tip, standalone, dir)	25m 17s
	7h 3m 48s

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