Update git submodules

* Update docs/submodules/fuel from branch 'master'
  - Merge "lib.sh: Reuse /tmp/mcp.rsa if present"
  - lib.sh: Reuse /tmp/mcp.rsa if present

    Long-term, /tmp/mcp.rsa should be moved to a persistent location [1],
    and made configurable via env var / other mechanisms.
    This will allow us to:
    - use an existing keypair (provided by end-user in expected path);
    - login to previous deployment machines (e.g. to cleanup UEFI boot
      entries before destroying the cluster and rebuilding it);
    - split deploy in re-entrant stages (salt master only, cluster nodes
      only; similar to old Fuel, where we could reuse old Fuel VM);

    [1] https://jira.opnfv.org/browse/FUEL-280

    Change-Id: I1e53321ed1cfc217ff95e809c867fa3370c479c9
    Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>

diff --git a/docs/submodules/fuel b/docs/submodules/fuel
index da551c0..7a38c0d 160000 (submodule)
--- a/docs/submodules/fuel
+++ b/docs/submodules/fuel
@@ -1 +1 @@
-Subproject commit da551c09038403de443d2eb563c91f42ad4d0f22
+Subproject commit 7a38c0d5f2b544bea0b5bcf755747f1fd04e5814