<!--- 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 -->
The `ssh_opts` parameter relies on setting environment variables for git, such as GIT_SSH. Git did not recognize this environment variable until version 2.3.0 (see https://git-scm.com/docs/git/2.3.0), and many contemporary OSes (RHEL 7, CentOS7) include older versions of Git (1.8.3.1).

It would be useful to provide a warning in this case, similar to the warning for the `depth` parameter. E.g. "Your git version is too old to support the ssh_opts argument."

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
git.py
source control, git module

##### ADDITIONAL INFORMATION
<!--- Describe how the feature would be used, why it is needed and what it would solve -->
It would save users time when trying to troubleshoot failed git connections via SSH.

<!--- Paste example playbooks or commands between quotes below -->
```yaml
- name: clone a git repo
  git:
    repo: git@github.com:cherdt/hello_ansible.git
    dest: /opt/hello_ansible
    version: master
    ssh_opts: "{{-o IdentityFile=github_id_rsa}}"
```

<!--- HINT: You can also paste gist.github.com links for larger files -->

description:
            - Path to git executable to use. If not supplied,
              the normal mechanism for resolving binary paths will be used.
        type: path
        version_added: "1.4"
    bare:
        description:
            - If C(yes), repository will be created as a bare repo, otherwise
              it will be a standard repo with a workspace.
        type: bool
        default: 'no'
        version_added: "1.4"
    umask:
        description:
            - The umask to set before doing any checkouts, or any other
              repository maintenance.
        type: raw
        version_added: "2.2"
    recursive:
        description:
            - If C(no), repository will be cloned without the --recursive
              option, skipping sub-modules.
        type: bool
        default: 'yes'
        version_added: "1.6"
    single_branch:
        description:
            - Clone only the history leading to the tip of the specified revision.
        type: bool
        default: 'no'