Update git submodules

* Update docs/submodules/apex from branch 'master'
  - Merge "Adding libguestfs-tools as dependency"
  - Adding libguestfs-tools as dependency

      Needed for virt-customize the images

    Change-Id: Ide3fff2c6b850047add6eeed4082c518c36e6e74
    Signed-off-by: Ricardo Noriega <rnoriega@redhat.com>

diff --git a/docs/submodules/apex b/docs/submodules/apex
index 26e6de0..b2905df 160000 (submodule)
--- a/docs/submodules/apex
+++ b/docs/submodules/apex
@@ -1 +1 @@
-Subproject commit 26e6de0b9d2b60f72380949dcf319e00e03daa95
+Subproject commit b2905df3252698437d66fb8ff368d1ef28230e63