Update git submodules

* Update os-net-config from branch 'master'
  - Merge "Remove mox usage"
  - Remove mox usage
    
    Introduce ''stub_out'' method to base test class
    
    We would like to fully remove mox from the test tree.
    Even for tests that don't use mox's validation, many of
    them are using the symbol patching with self.stubs.Set. We can
    do the same thing with the monkeypatch fixture instead.
    
    This introduces self.stub_out to os_net_config/tests/base.py
    and modifies the self.stubs.Set usage to self.stub_out.
    
    We also remove the mox dependency.
    
    Change-Id: Ib2fba5ecbbca5526bce2a4405704efb69ab7b5f0
    Signed-off-by: Charles Short <zulcss@gmail.com>