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##### SUMMARY
<!--- Describe the new feature/improvement briefly below -->
Add a --cacheonly option to the ansible yum module, similar to the --downloadonly option.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
lib/ansible/modules/packaging/os/yum.py

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->
We have a group of Oracle servers that have no repository management server.  They update directly from Oracle's repositories.  Our thought is to do a "yum update --downloadonly" on all dev and prod servers.  Then we can update the dev servers first using "yum update --cacheonly" to test then updated and run the same command on the prod at a later time to make them consistent with the dev.
<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

<!--- HINT: You can also paste gist.github.com links for larger files -->

lock_timeout:
    description:
      - Amount of time to wait for the yum lockfile to be freed.
    required: false
    default: 30
    type: int
    version_added: "2.8"
  install_weak_deps:
    description:
      - Will also install all packages linked by a weak dependency relation.
      - "NOTE: This feature requires yum >= 4 (RHEL/CentOS 8+)"
    type: bool
    default: "yes"
    version_added: "2.8"
  download_dir:
    description:
      - Specifies an alternate directory to store packages.
      - Has an effect only if I(download_only) is specified.
    type: str
    version_added: "2.8"
  install_repoquery:
    description:
      - If repoquery is not available, install yum-utils. If the system is
        registered to RHN or an RHN Satellite, repoquery allows for querying
        all channels assigned to the system. It is also required to use the
        'list' parameter.
      - "NOTE: This will run and be logged as a separate yum transation which
        takes place before any other installation or removal."
      - "NOTE: This will use the system's default enabled repositories without
        regard for disablerepo/enablerepo given to the module."