Update git submodules

Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "[maas] Enable back IPv6 for MaaS node"
  - [maas] Enable back IPv6 for MaaS node

    IPv6 has been disabled recently by default to reduce the attack
    surface of the system, however MaaS rackd service relies on other
    libraries that require an INET6 socket by design.

    Change-Id: I6c633e9790e75d53437f400790d0e528f0a792b3
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>