update ZFS to 2.0.4

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

diff --git a/submodules/zfsonlinux b/submodules/zfsonlinux
index 363c009381207615ba5880124e195c1263223add..28dd83391be7921ac561dae1bb2299f613419251 160000 (submodule)
--- a/submodules/zfsonlinux
+++ b/submodules/zfsonlinux
@@ -1 +1 @@
-Subproject commit 363c009381207615ba5880124e195c1263223add
+Subproject commit 28dd83391be7921ac561dae1bb2299f613419251