copyFileContent broken on zfs (in some cases)

[codyps]

See moby/moby#41866

Basically, need to add EINVAL on this line:

continuity/fs/copy_linux.go

Line 90 in 1805252

if (err != unix.ENOSYS && err != unix.EXDEV) || !first {

Also worth considering if any error should cause the fallback.

I haven't isolated the kernel version/zfs version that causes the issue. My kernel & zfs version are posted in the moby ticket linked above.