Update git submodules

Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "[netconfig] APT: Prefer ipv4 connections over ipv6"
  - [netconfig] APT: Prefer ipv4 connections over ipv6

    Ubuntu prefers ipv6 connections therefore in some networks, this
    breaks software updates (it does a AAAA DNS lookup before A record
    lookups). Let's prefer old style ipv4 connections over the new ipv6 in
    order to save some processing and resource utilization.

    Based on previous work from [1] (but without /etc/gai.conf, only APT).

    [1] https://review.openstack.org/#/c/462502/

    JIRA: FUEL-321

    Change-Id: Ic3dff3baa1c0be9ac95972557d6a2d26641bfe1b
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>