<!--- 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 -->

installed = self.base.sack.query().installed()
        if installed.filter(name=pkg):
            return True
        else:
            return False
    def _is_newer_version_installed(self, pkg_name):
        candidate_pkg = self._packagename_dict(pkg_name)
        if not candidate_pkg:
            
            
            return False
        installed = self.base.sack.query().installed()
        installed_pkg = installed.filter(name=candidate_pkg['name']).run()
        if installed_pkg:
            installed_pkg = installed_pkg[0]
            
            evr_cmp = self._compare_evr(
                installed_pkg.epoch, installed_pkg.version, installed_pkg.release,
                candidate_pkg['epoch'], candidate_pkg['version'], candidate_pkg['release'],
            )
            if evr_cmp == 1:
                return True
            else:
                return False
        else:
            return False
    def _mark_package_install(self, pkg_spec, upgrade=False):