Update git submodules

* Update docs/submodules/promise from branch 'master'
  - Fix the wrong image path

    The images are put in the dir /home/opnfv/functest/images now.

    Change-Id: I15b41782cd7a7372bdb962da575edc5d1b54d509
    Signed-off-by: Linda Wang <wangwulin@huawei.com>

diff --git a/docs/submodules/promise b/docs/submodules/promise
index a6ff265..fe5b31f 160000 (submodule)
--- a/docs/submodules/promise
+++ b/docs/submodules/promise
@@ -1 +1 @@
-Subproject commit a6ff2653735c28bf478a1dda713bd1edea6cf378
+Subproject commit fe5b31f939c3b600fb46c30d427eb08a89f7ea21