Bug 1094730 - [Flame][v2.1][Contacts] after merging a new contact with I...

...CE contacts, the setting of ICE contacts will be cleared.
This is the code we use in other places, and was thinking on making it a bit secure, `setItem` is asynchronous, should we wrap it into a promise and then chain it with the `modifyICEInDS` method that returns a promise too?