Update git submodules

Update git submodules

* Update docs/submodules/netvirt from branch 'master'
  to 4f2208b0bff77c8d06f12d8d3f9a600a8be2c33e
  - Return the tagged ELAN instance

    ElanUtils::updateOperationalDataStore() is given an ElanInstance to
    update, but because YANG instances are immutable, it has to create a
    new one to add the ELAN tag. As a result, calling code has to waiting
    for the surrounding MD-SAL transaction to finish, and then retrieve
    the updated ElanInstance from the MD-SAL... This patch makes the
    update method return the updated ElanInstance, potentially avoiding a
    MD-SAL round-trip and enabling more asynchronous operations.

    Change-Id: Ia83d65b2d0953c97976d37af0bb4299841925b8e
    Signed-off-by: Stephen Kitt <skitt@redhat.com>