Update git submodules

Update git submodules

* Update docs/submodules/sdnvpn from branch 'stable/euphrates'
  - Fix instance boot when metadata exists

    The way that a instance is considered as UP is pretty
    strict and returns ERROR in case of instances with userdata

    This patch differentiates the instances that are supposed to
    boot till login prompt and those with userdata parameter

    JIRA: SDNVPN-177

    Change-Id: Ic4755366df006669475c90cc0693ac802256f379
    Signed-off-by: tomsou <soth@intracom-telecom.com>
    (cherry picked from commit a6e207c16430055eba8bcc8586b09a7081db3d04)