libsirenia: Skip vsock tests.

These tests were originally in chromeos-base/sirenia but were moved to
libsirenia and the test flags need to move as well.

BUG=chromium:1158247
TEST=FEATURES=test emerge-${BOARD} libsirenia

Change-Id: I4646b1e68156a31df937426cbacba7963d517096
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/2588841
Reviewed-by: Nicole Anderson-Au <nvaa@google.com>
Commit-Queue: Allen Webb <allenwebb@google.com>
Tested-by: Allen Webb <allenwebb@google.com>
2 files changed