Update git submodules

* Update docs/submodules/promise from branch 'master'
  - Fix image name iteration

    Create a promise image depending on the glance image path.
    Due to glance image listing returning image names, looking
    for an image based on an image path is always false, thus
    its relevant to only look for the glance image name and if it exists
    to use its ID, if not to create a new image given the promise
    image name.

    JIRA: ARMBAND-223

    Change-Id: I2d1347807335f2c7e9d62f1a6c75fb48de6cf448
    Signed-off-by: Catalina Focsa <catalina.focsa@enea.com>

diff --git a/docs/submodules/promise b/docs/submodules/promise
index e5691c0..2acf978 160000 (submodule)
--- a/docs/submodules/promise
+++ b/docs/submodules/promise
@@ -1 +1 @@
-Subproject commit e5691c01975e9a3867a17c4fd9b4427bb15f0f10
+Subproject commit 2acf978923acb4c89785331046e293b957e88dfa