<!--- 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 -->

cloning = False
    cwd = None
    tag = False
    if remote == module.params['repo']:
        cloning = True
    elif remote == 'file://' + os.path.expanduser(module.params['repo']):
        cloning = True
    else:
        cwd = dest
    if version == 'HEAD':
        if cloning:
            
            cmd = '%s ls-remote %s -h HEAD' % (git_path, remote)
        else:
            head_branch = get_head_branch(git_path, module, dest, remote, bare)
            cmd = '%s ls-remote %s -h refs/heads/%s' % (git_path, remote, head_branch)
    elif is_remote_branch(git_path, module, dest, remote, version):
        cmd = '%s ls-remote %s -h refs/heads/%s' % (git_path, remote, version)
    elif is_remote_tag(git_path, module, dest, remote, version):
        tag = True
        cmd = '%s ls-remote %s -t refs/tags/%s*' % (git_path, remote, version)
    else:
        
        
        return version
    (rc, out, err) = module.run_command(cmd, check_rc=True, cwd=cwd)
    if len(out) < 1: