Update git submodules

* Update docs/submodules/snaps from branch 'master'
  - Refactoring of ImageSettings to extend ImageConfig

    ImageSettings and glance_utils have a runtime cyclical
    dependency. This patch reduces this dependency and
    deprecates the ImageSettings class.

    JIRA: SNAPS-217

    Change-Id: I09f34531366f2a5bd3202c9cbbdef878b2542abe
    Signed-off-by: spisarski <s.pisarski@cablelabs.com>

diff --git a/docs/submodules/snaps b/docs/submodules/snaps
index 792a01b..4cad4f7 160000 (submodule)
--- a/docs/submodules/snaps
+++ b/docs/submodules/snaps
@@ -1 +1 @@
-Subproject commit 792a01b6592b320b80bdc7465247b0fcb19f1264
+Subproject commit 4cad4f7d1f53189900f9024fa5478e98a64d3760