incus: Handle non-existent home directory #377

Job	Run time
Code	4m 11s
Client (1.20.x, ubuntu-latest)	1m 23s
System (1.20.x, cluster, dir)	4m 10s
Client (1.20.x, macos-latest)	1m 23s
Documentation	4m 11s
System (1.20.x, cluster, btrfs)	4m 9s
Client (1.20.x, windows-latest)	2m 12s
System (1.20.x, cluster, lvm)	4m 11s
System (1.20.x, cluster, zfs)	4m 10s
System (1.20.x, cluster, ceph)	4m 10s
System (1.20.x, cluster, random)	4m 7s
System (1.20.x, standalone, dir)	4m 10s
System (1.20.x, standalone, btrfs)	4m 9s
System (1.20.x, standalone, lvm)	4m 8s
System (1.20.x, standalone, zfs)	4m 8s
System (1.20.x, standalone, ceph)	4m 7s
System (1.20.x, standalone, random)	4m 12s
System (stable, cluster, dir)	4m 8s
System (stable, standalone, dir)	4m 10s
System (tip, cluster, dir)	4m 1s
System (tip, standalone, dir)	4m 8s
	1h 19m 38s

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