update ZFS On Linux submodule to 0.8.3

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

diff --git a/submodules/zfsonlinux b/submodules/zfsonlinux
index a18306641a7fe863e323b5f1d92377cc8b7f9bed..943c54360ffbdf9d64cb7025fd75b66e02627c67 160000 (submodule)
--- a/submodules/zfsonlinux
+++ b/submodules/zfsonlinux
@@ -1 +1 @@
-Subproject commit a18306641a7fe863e323b5f1d92377cc8b7f9bed
+Subproject commit 943c54360ffbdf9d64cb7025fd75b66e02627c67