The EtcdMain function in integration tests is designed to launch an etcd
instance only when running in a bazel test. For non-bazel, we rely on
hack/make-rules/test-integration.sh to bring up the etcd instance.
This patch fixes the following in EtcdMain:
1. If etcd is not found in ${RUNFILES_DIR} then look in ${PATH}.
2. Try to connect to the etcd started by `make test-integraion`; if it
is up, then don't start etcd.
3. Gracefully shut down etcd after tests.
4. Get a port from the OS instead of deriving it from argv[0].
5. Don't use sync.Once.
The benefit of this change is that integration tests work with `go test`
as well as `make test-integration` without users needing to do anything
special. That makes it much easier to pass go testing flags to tests and
integrate with IDEs.
abstract out etcd server creation
test/integration/framework: cleanup master_utils.go
kube-apiserver: move StartTestServer tests into test/integration/master
Fix the failing scale test
kube-apiserver's TestServer now returns a struct instead of individual values
