title: Deployment Manager: Operation failed because another operation was already in progress
body: <p>I want to create two databases in one cloudsql instance.
  But if it is written in the following way it will result in an error.</p>
  
  <pre><code>resources:
  - name: test-instance
    type: sqladmin.v1beta4.instance
    properties:
      region: us-central
      backendType: SECOND_GEN
      instanceType: CLOUD_SQL_INSTANCE
      settings:
        tier: db-f1-micro
  - name: test_db1
    type: sqladmin.v1beta4.database
    properties:
      instance: $(ref.test-instance.name)
      charset: utf8mb4
      collation: utf8mb4_general_ci
  - name: test_db2
    type: sqladmin.v1beta4.database
    properties
      instance: $(ref.test-instance.name)
      charset: utf8mb4
      collation: utf8mb4_general_ci
  </code></pre>
  
  <p>output:</p>
  
  <pre><code>ERROR: (gcloud.deployment-manager.deployments.create) Error in Operation 
  [operation-********]
  - code: RESOURCE_ERROR
    location: /deployments/sample-deploy/resources/test_db2
     message:
  '{"ResourceType":"sqladmin.v1beta4.database","ResourceErrorCode":"403","ResourceErrorMessage":{"code":403,"errors":[{"domain":"global","message":"Operation
      failed because another operation was already in progress.","reason":"operationInProgress"}],"message":"Operation
      failed because another operation was already in progress.","statusMessage":"Forbidden","requestPath":"https://www.googleapis.com/sql/v1beta4/projects/****/instances/test-instance/databases","httpMethod":"POST"}}'
  </code></pre>
  
  <p>Please tell me what to do to resolve the error.</p>