net-test: fix mixed build R+T lack of tcp_default_init_rwnd on old 4.14 kernels am: 913b27b357 am: dc6844a47d Original change: https://googleplex-android-review.googlesource.com/c/kernel/tests/+/18718523 Change-Id: Ia3cbaf40adad80e2bfc4c1825da64b3da645a93a Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>