clean-up "nolint" comments, remove unused ones

- fix "nolint" comments to be in the correct format (`//nolint:<linters>[,<linter>`
  no leading space, required colon (`:`) and linters.
- remove "nolint" comments for errcheck, which is disabled in our config.
- remove "nolint" comments that were no longer needed (nolintlint).
- where known, add a comment describing why a "nolint" was applied.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

oci/spec_opts_linux_test.go

@@ -31,7 +31,7 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// nolint:gosec
+//nolint:gosec
 func TestWithUserID(t *testing.T) {
 	t.Parallel()
 
@@ -86,7 +86,7 @@ guest:x:405:100:guest:/dev/null:/sbin/nologin
 	}
 }
 
-// nolint:gosec
+//nolint:gosec
 func TestWithUsername(t *testing.T) {
 	t.Parallel()
 
@@ -148,7 +148,7 @@ guest:x:405:100:guest:/dev/null:/sbin/nologin
 
 }
 
-// nolint:gosec
+//nolint:gosec
 func TestWithAdditionalGIDs(t *testing.T) {
 	t.Parallel()
 	expectedPasswd := `root:x:0:0:root:/root:/bin/ash