samba4: security bump to version 4.6.11

samba4: security bump to version 4.6.11

Fixes the following security issues:

 - CVE-2017-14746:
   All versions of Samba from 4.0.0 onwards are vulnerable to a use after
   free vulnerability, where a malicious SMB1 request can be used to
   control the contents of heap memory via a deallocated heap pointer. It
   is possible this may be used to compromise the SMB server.

 - CVE-2017-15275:
   All versions of Samba from 3.6.0 onwards are vulnerable to a heap
   memory information leak, where server allocated heap memory may be
   returned to the client without being cleared.

   There is no known vulnerability associated with this error, but
   uncleared heap memory may contain previously used data that may help
   an attacker compromise the server via other methods. Uncleared heap
   memory may potentially contain password hashes or other high-value
   data.

For more details, see the release notes:
https://www.samba.org/samba/history/samba-4.6.11.html

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>