ovs_appctl_compgen: Remove the completion for remote.

For now, do not complete on 'remote'.  May be added in the
future.

Signed-off-by: Yeqiao Wang <ee07b291@gmail.com>
ovs-appctl-compgen: Rename the program and add test file.

Signed-off-by: Yeqiao Wang <ee07b291@gmail.com>