<!--- Verify first that your feature was not already discussed on GitHub -->
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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 -->

"""Return a dictionary of information for the package."""
        
        
        result = {
            'name': package.name,
            'arch': package.arch,
            'epoch': str(package.epoch),
            'release': package.release,
            'version': package.version,
            'repo': package.repoid}
        result['nevra'] = '{epoch}:{name}-{version}-{release}.{arch}'.format(
            **result)
        if package.installtime == 0:
            result['yumstate'] = 'available'
        else:
            result['yumstate'] = 'installed'
        return result
    def _packagename_dict(self, packagename):