Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "Discover computes after they are registered"
  - Discover computes after they are registered

    The "nova hypervisor-list" won't work (i.e. will result in an empty list)
    until discover_hosts is launched with compute nodes on board.

    Change-Id: I942c69645731b59a5cb9e5cf39a89b84def96b12
    Signed-off-by: Michael Polenchuk <mpolenchuk@mirantis.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index 941a31e..18e2ece 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit 941a31e1e7f64f38a487b4e493bc25fdf29657da
+Subproject commit 18e2ece7f9f1aba3a4bdc031020b97f40e65fb3c