Update git submodules

* Update nova from branch 'master'
  to fb992ef376573e2f1bc5e65199074a70373899ce
  - Merge "Make RBD Tpool usage conditional"
  - Make RBD Tpool usage conditional

    When running in eventlet mode we keep the original eventlet.tpool usage
    but when running in threading mode we call the functions directly on the
    thread of the caller.

    Signed-off-by: Balazs Gibizer <gibi@redhat.com>
    Change-Id: I08f257d49c87d0d8a87127f61157b1b0b5ca7b3c

diff --git a/nova b/nova
index 3d8513301bccd368da822cd32b65cad23da9961f..fb992ef376573e2f1bc5e65199074a70373899ce 160000 (submodule)
--- a/nova
+++ b/nova
@@ -1 +1 @@
-Subproject commit 3d8513301bccd368da822cd32b65cad23da9961f
+Subproject commit fb992ef376573e2f1bc5e65199074a70373899ce