Deflake doDualStackProvisioning

The current implementation is flaky because DHCP packets received while
waiting for IPv6 provisioning are lost.

Bug: 159298830
Test: atest IpClientIntegrationTest#testDualStackProvisioning \
          --rerun-until-failure 50
Change-Id: I13dc66aff425650054aab5100c7ba6fe97f07e3a
2 files changed