Require Go 1.17, bump x/sys and x/net

1. bump golang.org/x/sys to v0.6.0;
2. bump golang.org/x/net to v0.8.0
3. require Go 1.17.

Newer x/sys is needed to fix [1].

Go 1.17 is needed because x/sys/unix is using unsafe.Slice which
requires go1.17 or later.

This reuses parts of main commit a0f8847e2a.

[1] https://github.com/opencontainers/runc/issues/3715

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

.github/workflows/test.yml

@@ -21,7 +21,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        go-version: [1.16.x, 1.17.x]
+        go-version: [1.17.x]
         rootless: ["rootless", ""]
         race: ["-race", ""]
         criu: [""]