LU-16835 target: server_ioctl() should return ENOTTY

LU-16835 target: server_ioctl() should return ENOTTY

server_ioctl() returns EOPNOTSUPP when ioctl cmd
is not supported. This will confuse e2fsprogs >= 1.47
as it's trying to get/set fs label using
FS_IOC_GETFSLABEL and FS_IOC_SETFSLABEL ioctl.

If the cmd is not supported we really should return
ENOTTY which means "Inappropriate ioctl for device".

Change-Id: Ibca0e6ad9a5c19cc7bd55ebd96cf32af05cf0fb6
Test-Parameters: trivial
Fixes: d5be104cc9 ("LU-11355 lustre: enable fstrim on lustre device")
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51072
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>