Update git submodules

* Update keystone from branch 'master'
  to 19e1b3fc91d960de232dbc4d356e681ad12317d1
  - Merge "Drop unused tempest from test requirements"
  - Drop unused tempest from test requirements

    None of the tests implemented in this repository depend on tempest.
    Also clean up the note about old pip's behavior because recent release
    of pip does not care the package orders in requirements files.

    Change-Id: I81deab4bb8b30d9b3edd3669b7d39e8ac3f5dcfe

diff --git a/keystone b/keystone
index c3bfa0924d82e52e9429575bcfeb8963f7df6dd8..19e1b3fc91d960de232dbc4d356e681ad12317d1 160000 (submodule)
--- a/keystone
+++ b/keystone
@@ -1 +1 @@
-Subproject commit c3bfa0924d82e52e9429575bcfeb8963f7df6dd8
+Subproject commit 19e1b3fc91d960de232dbc4d356e681ad12317d1