Bugfix: Fix collaborator selection on new collaborator shares

When typing text into the search box for new collaborators, selecting a user and a group with identical names was not possible.
This was due to the fact that when one (group or user) got selected, the other was excluded because of a matching name. Fixed by
including the share type (group or user) in matching.

https://github.com/owncloud/web/issues/1186
