Add optional podRepoUpdate flag in iosConfig

• Can be used to update the pod specs when running pod install in container generation. Flag is by default disabled and can be enabled in cauldron below.
  This flag was made to use in regen-container command - it generates the container with updating the pod specs during pod install and updates the cauldron with new version and yarnlocks.

{
  "containerGenerator": {
    "iosConfig": {
      "podRepoUpdate": true
    }
  }
}

or can be using in extra argument in create-container command
--extra '{"iosConfig": {"deploymentTarget": "11.0", "podRepoUpdate": true}}'