python: Whitelist CVE-2017-17522 CVE-2017-18207 CVE-2015-5652

One Windows-only CVE that cannot be fixed, and two CVEs
where upstream agreement is that they are not vulnerabilities.

(From OE-Core rev: 56d5b181)

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>