Using localSchemaFile connection refused

Issue Type: Bug

I am trying to get the extension to work with a minimal configuration.
```
// apollo.config.js
module.exports = {
service: {
localSchemaFile: './src/schema.graphql'
}
};
```

```
// src/schema.grphql
type Query {
hello: String
}

```
Server is running and I can reach it in the browser but VSCode insists that connection got refused. I even tried CORS with no effect.

`request to http://localhost:4000/graphql failed, reason: connect ECONNREFUSED 127.0.0.1:4000`

Extension version: 1.16.6
VS Code version: Code - Insiders 1.48.0-insider (eb1ca267d6a478734bd7f3d629ac9b80926ee9d1, 2020-07-21T12:39:31.001Z)
OS version: Darwin x64 18.7.0

System Info

|Item|Value|
|---|---|
|CPUs|Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz (8 x 2800)|
|GPU Status|2d_canvas: enabled
flash_3d: enabled
flash_stage3d: enabled
flash_stage3d_baseline: enabled
gpu_compositing: enabled
metal: disabled_off
multiple_raster_threads: enabled_on
oop_rasterization: enabled
opengl: enabled_on
protected_video_decode: unavailable_off
rasterization: enabled
skia_renderer: disabled_off_ok
video_decode: enabled
webgl: enabled
webgl2: enabled|
|Load (avg)|62, 91, 88|
|Memory (System)|16.00GB (0.40GB free)|
|Process Argv|-psn_0_413797|
|Screen Reader|no|
|VM|0%|

Reproduce the minimal configuration from apollo.config.js using src/schema.graphql and the reported localhost:4000/graphql request. Start by tracing how the VS Code extension handles localSchemaFile and compare the configured schema path with the supplied filename. Done means the minimal local-schema setup no longer attempts the refused connection, with the behavior verified against this example.

Written by the indexing model from the issue text.