<!--- 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 -->

rc, out, err = self.module.run_command(cmd, environ_update=lang_env)
        if rc == 1:
            for spec in items:
                
                if ('://' in spec and ('No package %s available.' % spec in out or 'Cannot open: %s. Skipping.' % spec in err)):
                    err = 'Package at %s could not be installed' % spec
                    self.module.fail_json(changed=False, msg=err, rc=rc)
        res['rc'] = rc
        res['results'].append(out)
        res['msg'] += err
        res['changed'] = True
        if ('Nothing to do' in out and rc == 0) or ('does not have any packages' in err):
            res['changed'] = False
        if rc != 0:
            res['changed'] = False
            self.module.fail_json(**res)
        
        
        
        
        
        if 'No space left on device' in (out or err):
            res['changed'] = False
            res['msg'] = 'No space left on device'
            self.module.fail_json(**res)
        
        
        
        return res
    def install(self, items, repoq):