Reduce e2e test parrallelism from 64 to 32 (#2019)

One theory is that we're running too many tests
for the controller/control plane to manage at any given
point and time, and things are timing out and that's why we're getting so many flakes.

build/e2e-image/e2e.sh

@@ -20,5 +20,5 @@ set -e
 echo "installing current release"
 DOCKER_RUN= make install FEATURE_GATES='"'$FEATURES'"'
 echo "starting e2e test"
-DOCKER_RUN= make test-e2e ARGS=-parallel=64 FEATURE_GATES='"'$FEATURES'"'
+DOCKER_RUN= make test-e2e ARGS=-parallel=32 FEATURE_GATES='"'$FEATURES'"'
 echo "completed e2e test"