Fix Studio snapshot dependency check

The dependency check seems to be done on the already installed package instead of the remote one.

Steps to reproduce (on 8.1):

• start with a Nuxeo with no package
• link it to a Studio project using target platform 8.1, with no package
• install it using the "update" hot reload button from the admin center => ok
• on Studio side, add the "virtual navigation" package as a dependency, for instance
• install it again using the "update" hot reload button from the admin center => KO

The dependency check should warn that the virtual navigation package is not present.