Call: update ContactMethod when peerName is set

The ContactMethod uses the peerName as an alternative name; however
it was only getting this info via the PhoneDirectoryModel during
slotCallAdded and this info was not always ready at that moment.

Change-Id: Ic00f5c8afbf62f91ac045ce8f2c42ffb9102e6a5
Tuleap: #307