look for version in bazel-bin

bazel-bin and bazel-genfiles have pointed to the same location since
0.25. -genfiles is deprecated.

This was test running:

../test-infra/scenarios/kubernetes_bazel.py --push

With bazel version 2.2.0 and 0.23.2.

Issue: bazelbuild/bazel#8651

scenarios/kubernetes_bazel.py

@@ -116,7 +116,13 @@ def echo_result(res):
 
 def get_version():
     """Return kubernetes version"""
-    with open('bazel-genfiles/version') as fp:
+    # The check for version in bazel-genfiles can be removed once everyone is
+    # off of versions before 0.25.0.
+    # https://github.com/bazelbuild/bazel/issues/8651
+    if os.path.isfile('bazel-genfiles/version'):
+        with open('bazel-genfiles/version') as fp:
+            return fp.read().strip()
+    with open('bazel-bin/version') as fp:
         return fp.read().strip()
 
 def get_changed(base, pull):