Explicit dependencies fail inside of case statements

[rebeccaskinner]

This is broken:

file.content "foo" {
  destination = "foo"
  content = "foo"
}

switch "touch-file" {
  default {
    task.query "touch-file" {
      query = "touch file.txt"
      depends = ["file.content.foo"]
    }
  }
}

Probably because dependency resolution isn't addressing ancestor nodes for explicit dependencies, we should probably look at the code that's being used by lookup and param dependency generation and either put that in getDepends or move the logic to the actual walk function.

[rebeccaskinner]

Closed by #391