lxd/storage: Fix check for direct I/O write support #11758

Job	Run time
Client (1.22.x, ubuntu-latest)	33s
Code	11m 16s
Client (1.22.x, macos-latest)	22s
Client (1.22.x, windows-latest)	2m 57s
Documentation	4m 4s
System (1.22.x, cluster, dir)	11m 57s
System (1.22.x, cluster, btrfs)	12m 45s
System (1.22.x, cluster, lvm)	16m 11s
System (1.22.x, cluster, zfs)	12m 38s
System (1.22.x, cluster, ceph)	16m 42s
System (1.22.x, cluster, random)	13m 7s
System (1.22.x, standalone, dir)	25m 42s
System (1.22.x, standalone, btrfs)	25m 26s
System (1.22.x, standalone, lvm)	37m 19s
System (1.22.x, standalone, zfs)	41m 17s
System (1.22.x, standalone, ceph)	1h 28m 49s
System (1.22.x, standalone, random)	33m 25s
System (stable, cluster, dir)	10m 26s
System (stable, standalone, dir)	23m 58s
Trigger snap edge build	0s
Tiobe TICS	0s
	6h 28m 54s

Provide feedback