[BUG] common folder is checked twice when reference to external common component

Bug Report Checklist

• [ x] Have you provided a full/minimal spec to reproduce the issue?
• [ x] Have you validated the input using an OpenAPI validator (example)?
• [ x] What's the version of OpenAPI Generator used? --> latest (nightlybuild 09052019)
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

use remote reference in common folder does not wok

In principal specifications, i added a reference to common specification schema:
$ref: './components/errors.yaml#/components/responses/400'
error message
[main] WARN o.o.codegen.utils.ModelUtils - Failed to get the schema name: ./components/components/errors.yaml#/components/schemas/Error
=>common folder is checked twice

openapi-generator version

latest SNAPSHOT version : nightly build 09052019

OpenAPI declaration file content or url

#principal specifications: /some-api.yaml
openapi: 3.0.0
info:
title: Test
version: 1.0.0

paths:
/value:
get:
operationId: getValues
responses:
"200":
description: OK
content:
application/json:
schema:
$ref: '#/components/schemas/ComponentA'
"400":
$ref: './components/errors.yaml#/components/responses/400'

components:
schemas:
ComponentA:
type: object
properties:
someAtt:
description: some attribute
type: string

common specifications /components/errors.yaml

components:
schemas:
Error:
type: object
title: SomeError
description: Error details
properties:
name:
type: string
description: Human readable, unique name of the error.
responses:
"400":
description: Bad Request
content:
application/json:
schema:
$ref: '#/components/schemas/Error'

Command line used for generation

java -jar ./openapi-generator-cli.jar generate -g spring -i some-api.yaml -c some-api-java.json -o ./generated/some-api

Reproduce the issue with some-api.yaml, components/errors.yaml, and the Java CLI command using the spring generator. Start at the ModelUtils warning about the duplicated components path and trace external $ref resolution. Done means the external response resolves its Error schema without checking the common folder twice.