<!--- Verify first that your feature was not already discussed on GitHub -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### 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 -->

#
    
    
    
    
    
    
    
    
    yumdnf_argument_spec['argument_spec']['allowerasing'] = dict(default=False, type='bool')
    yumdnf_argument_spec['argument_spec']['nobest'] = dict(default=False, type='bool')
    module = AnsibleModule(
        **yumdnf_argument_spec
    )
    module_implementation = DnfModule(module)
    try:
        module_implementation.run()
    except dnf.exceptions.RepoError as de:
        module.fail_json(
            msg="Failed to synchronize repodata: {0}".format(to_native(de)),
            rc=1,
            results=[],
            changed=False
        )
if __name__ == '__main__':
    main()