CA-248125: Fix openvswitch-config-update plugin issue.
CA-248125: Fix openvswitch-config-update plugin issue.

1. When xapi restart, the plugin should report no change of SDN controller.
2. Do not print iptablectl output to ensure xapi correctly handles plugin output.

Signed-off-by: Hui Zhang <1290dea41121f0a9caa715ba0808e38da438ab06@citrix.com>

euanh/xen-api,euanh/xen-api,Frezzle/xen-api,Frezzle/xen-api,Frezzle/xen-api,srowe/xen-api,Frezzle/xen-api,euanh/xen-api,Frezzle/xen-api,euanh/xen-api,srowe/xen-api,euanh/xen-api,euanh/xen-api,srowe/xen-api,srowe/xen-api,srowe/xen-api