Add --hostport to run-container.

This helps as a starting point to show a single-machine container.
Its easier to use this as an example to show where host port mapping breaks and move on to
services.

contrib/completions/bash/kubectl

@@ -530,6 +530,7 @@ _kubectl_run-container()
     flags+=("--generator=")
     flags+=("--help")
     flags+=("-h")
+    flags+=("--hostport=")
     flags+=("--image=")
     flags+=("--labels=")
     two_word_flags+=("-l")