Add the default Homebrew path for OpenSSL certs on OS X

Per the discussion at https://github.com/ansible/ansible-modules-extras/issues/82, the fix for that issue belongs here. This is merely a reiterated verified fix submitted by @sivel in that issue.

Perhaps this is the right place to discuss a more bullet-proof approach on OS X. Perhaps something like Homebrew itself does when installing OpenSSL: https://github.com/Homebrew/homebrew/blob/master/Library/Formula/openssl.rb#L103-L111

```
keychains = %w[
      /Library/Keychains/System.keychain
      /System/Library/Keychains/SystemRootCertificates.keychain
    ]

openssldir.mkpath
(openssldir/"cert.pem").atomic_write `security find-certificate -a -p #{keychains.join(" ")}`
```

This just dumps the root certificates from OS X's keychain into /usr/local/etc/openssl. Perhaps ansible could do this during installation too?