Update git submodules

* Update docs/submodules/kvmfornfv from branch 'stable/danube'
  - [fuel-plugin] Set default grub entry for kernel

    JIRA: KVMFORNFV-77
    Change-Id: Ibb764cd5fa9822d337ce6f948bff8213c1caa7eb
    Signed-off-by: Paul Vaduva <Paul.Vaduva@enea.com>
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>
    (cherry picked from commit e797a9f954797949f676a46f5c9ceb31874f919a)

diff --git a/docs/submodules/kvmfornfv b/docs/submodules/kvmfornfv
index 8815494..4375b68 160000 (submodule)
--- a/docs/submodules/kvmfornfv
+++ b/docs/submodules/kvmfornfv
@@ -1 +1 @@
-Subproject commit 8815494ebba1bbb37ab0a9f9700f5dfb33cf12fb
+Subproject commit 4375b689ffa0f2f37c04fef7c25aaf9473ba8582