Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Local Documentation Builds

        This adds configuration for performing local documentation builds
        with the following simple command:

        tox -e docs

    Change-Id: I84d69542d8c603e72d4af460834134d9711ac537
    Signed-off-by: Aric Gardner <agardner@linuxfoundation.org>

diff --git a/docs/submodules/samplevnf b/docs/submodules/samplevnf
index 3afd384..4d59d35 160000 (submodule)
--- a/docs/submodules/samplevnf
+++ b/docs/submodules/samplevnf
@@ -1 +1 @@
-Subproject commit 3afd384b7e68a3cd29f4d2cdf39785f8441d0b6f
+Subproject commit 4d59d3530d1c41734f15423142e64eb9c929c717