Fix double completion bug

[julienduchesne]

woops
Closes #122

[Duologic]

This fixes it for one of my use cases, but I have one more that still shows doubles with this PR.

[Duologic]

And I can now reproduce it, just need one more import layer 😿

local g = import 'hello3.jsonnet';

{
  a: g.hello.<tab>,
}

// hello.jsonnet
{
  hello: {
    to: {
      the: 'world',
    },
  },
}

// hello2.jsonnet
{ hello: (import 'hello.jsonnet').hello }

// hello3.jsonnet
import 'hello2.jsonnet'