Pushing schema update of non-existing version hangs

[wwerner]

Steps to reproduce:

1. Create O/U/C/S/SV as in the first snippet
2. Update a schema version like in the second snippet

## Create master data

### Create Organization
POST http://localhost:9019/organizations
Content-Type: application/json

{
  "organizationId": "",
  "name": "Vlingo",
  "description": "Vlingo Organization"
}

> {% client.global.set('orgId', response.body.organizationId) %}


### Create Unit
POST  http://localhost:9019/organizations/{{orgId}}/units
Content-Type: application/json

{
  "organizationId": "{{orgId}}",
  "unitId": "",
  "name": "schemata",
  "description": "Schemata Unit"
}

> {% client.global.set('unitId', response.body.unitId) %}

### Create Context
POST http://localhost:9019/organizations/{{orgId}}/units/{{unitId}}/contexts
Content-Type: application/json

{
  "organizationId": "{{orgId}}",
  "unitId": "{{unitId}}",
  "contextId": "",
  "namespace": "io.vlingo.schemata",
  "description": "Schemata Context"
}

> {% client.global.set('contextId', response.body.contextId) %}

### Create Schema
POST http://localhost:9019/organizations/{{orgId}}/units/{{unitId}}/contexts/{{contextId}}/schemas
Content-Type: application/json

{
  "organizationId": "{{orgId}}",
  "unitId": "{{unitId}}",
  "contextId": "{{contextId}}",
  "schemaId": "",
  "category": "Event",
  "name": "SchemaDefined",
  "scope": "Public",
  "description": "Fired whenever a new schema is defined."
}

> {% client.global.set('schemaId', response.body.schemaId) %}


###
## Demo starts here

### Push schema by reference

POST http://localhost:9019/versions/Vlingo:schemata:io.vlingo.schemata:SchemaDefined:0.0.1
Content-Type: application/json

{
  "description": "Updated revision.",
  "specification": "event SchemaDefined { type eventType }",
  "previousVersion": "0.0.0"
}

> {% client.global.set('schemaVersionId', response.body.schemaVersionId) %}

### Update schema by reference

POST http://localhost:9019/versions/Vlingo:schemata:io.vlingo.schemata:SchemaDefined:1.0.1
Content-Type: application/json

{
  "description": "Updated revision.",
  "specification": "event SchemaDefined { type eventType\nlong version }",
  "previousVersion": "1.0.0"
}

> {% client.global.set('schemaVersionId', response.body.schemaVersionId) %}