Update git submodules

* Update manila from branch 'master'
  to cef2bd8af9ffec61b3869b03ffb52a6390d19b5f
  - Fix schema for all_tenants query parameter

    ... to resolve the following error in list snapshot API with the flag.

    ```
    Invalid input for field/attribute all_tenants. Value: ['1']. ['1'] is
    not of type 'boolean', 'string'
    ```

    Change-Id: Id8c83b87b0000c25ae4bcebdbe97d5e096def33c
    Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

diff --git a/manila b/manila
index 975e546f7be3b7c92cce3ef19614f9292c3f8b6e..cef2bd8af9ffec61b3869b03ffb52a6390d19b5f 160000 (submodule)
--- a/manila
+++ b/manila
@@ -1 +1 @@
-Subproject commit 975e546f7be3b7c92cce3ef19614f9292c3f8b6e
+Subproject commit cef2bd8af9ffec61b3869b03ffb52a6390d19b5f