Fix the jspm inspect registry:name when there are forks

Currently, this only shows top level dependencies.
This commit allows to show all the forks and what their parent
packages are.

This was previously discussed in PR #1968 as a new feature,
while it was actually a bug.

Example output:

    Installed versions of npm:d3

       d3 4.1.1 (^4.1.1)

       npm:d3-heatmap@1.2.1
         d3 3.5.17 (^3.5.16)

lib/install.js

@@ -944,7 +944,7 @@ function loadExistingRange(name, parent, inject) {
       });
     })
     .then(function(deps) {
-      return deps[name];
+      return parent ? deps[(new PackageName(parent)).exactName][name] : deps[name];
     });
   })
   .then(function(target) {