Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Adding index.rst for developer guide

    Change-Id: Id9ad242c5147a1dc15a181baa2c5bd886335921c
    Signed-off-by: Deepak S <deepak.s@linux.intel.com>

diff --git a/docs/submodules/samplevnf b/docs/submodules/samplevnf
index 12566df..48413cd 160000 (submodule)
--- a/docs/submodules/samplevnf
+++ b/docs/submodules/samplevnf
@@ -1 +1 @@
-Subproject commit 12566dfed5cd94c21fc1ad0b1a2fab51a3e952e9
+Subproject commit 48413cdea74b0fedfde4dac00951100b7d32580a