Update git submodules

* Update docs/submodules/samplevnf from branch 'master'
  - Merge "Initialize fields of outer IP header"
  - Initialize fields of outer IP header

    As it was non being initialized, fragment offset was sometimes non null.
    prox_ip_cksum_sw (as well as prox_ip_cksum_hw) require the hdr_checksum
    field to be initialized to 0.

    Change-Id: I3824682023782edb555982e558e5ae68062c3c9b
    Signed-off-by: Xavier Simonart <xavier.simonart@intel.com>

diff --git a/docs/submodules/samplevnf b/docs/submodules/samplevnf
index 25ffc70..dd77bd8 160000 (submodule)
--- a/docs/submodules/samplevnf
+++ b/docs/submodules/samplevnf
@@ -1 +1 @@
-Subproject commit 25ffc7091ffe7069e6b4aeed9a5a69aa034c58f9
+Subproject commit dd77bd89e11d84d378167468db85fb4ef35a0c7a