CA-118423: Fix the issue where a non-management bond was shown as discon...

...nected in XenCenter because the NICs tab was not refreshed when the properties of the new bond changed.

- Register a PIF CollectionChanged event, so the page is refreshed when a bond is added / deleted.
- Register the PIF PropertyChanged event to each PIF when the grid is populated; this ensures that all the PIFs displayed will be refreshed when their properties change.

Signed-off-by: Mihaela Stoica <mihaela.stoica@citrix.com>