Update git submodules

* Update docs/submodules/so.git from branch 'master'
  to 2a278fedffa02f01f9fbc059fc25eab103cd7986
  - Merge "Use base image for SO dockers"
  - Use base image for SO dockers

    ONAP now has a specific base image for all containers using Java. This
    commit uses this file instead of creating a base image only for SO.

    Issue-ID: SO-2694
    Signed-off-by: Sylvain Desbureaux <sylvain.desbureaux@orange.com>
    Change-Id: I9578e4d5556bd175ad65c6d2f9ce917997651c7a

diff --git a/docs/submodules/so.git b/docs/submodules/so.git
index 03117ff..2a278fe 160000 (submodule)
--- a/docs/submodules/so.git
+++ b/docs/submodules/so.git
@@ -1 +1 @@
-Subproject commit 03117ffcb30ef5735a46c72a5f7ba10cdb66dc37
+Subproject commit 2a278fedffa02f01f9fbc059fc25eab103cd7986