<!--- 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 -->

- yum
author:
    - Ansible Core Team
    - Seth Vidal (@skvidal)
    - Eduard Snesarev (@verm666)
    - Berend De Schouwer (@berenddeschouwer)
    - Abhijeet Kasurde (@Akasurde)
    - Adam Miller (@maxamillion)
'''
EXAMPLES = '''
- name: Install the latest version of Apache
  yum:
    name: httpd
    state: latest
- name: Install Apache >= 2.4
  yum:
    name: httpd>=2.4
    state: present
- name: Install a list of packages (suitable replacement for 2.11 loop deprecation warning)
  yum:
    name:
      - nginx
      - postgresql
      - postgresql-server
    state: present
- name: Install a list of packages with a list variable
  yum:
    name: "{{ packages }}"
  vars:
    packages: