Update git submodules

Update git submodules

* Update docs/submodules/snaps from branch 'master'
  - Fixed bug with regards to subnet lookups.
    Neutron returns all subnets regardless of visibility which cause problems
    within routers if there is another subnet with the same name attached to
    a different network.

    JIRA: SNAPS-304

    In addition, this patch contains two other minor fixes.
      launch_utils.py - raise an exception when the creator is not properly instantiated
      network.py - allow fixed IPs to be none.

    Change-Id: Ib343074d925be4592a713727a03d5b531890eada
    Signed-off-by: spisarski <s.pisarski@cablelabs.com>