update ZFS module to 2.2.0

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

diff --git a/submodules/zfsonlinux b/submodules/zfsonlinux
index 9e8946d4b952b01574f05a877098e7cb5c5ab7de..aa99285dda7f91add062b177fe1a811334fdd4fb 160000 (submodule)
--- a/submodules/zfsonlinux
+++ b/submodules/zfsonlinux
@@ -1 +1 @@
-Subproject commit 9e8946d4b952b01574f05a877098e7cb5c5ab7de
+Subproject commit aa99285dda7f91add062b177fe1a811334fdd4fb