Update git submodules

* Update docs/submodules/releng from branch 'master'
  - yardstick: Create jobs for Euphrates

    This change switches jobs to euphrates and removes danube jobs.

    Change-Id: I421b3927e05712a62409e768b1b6a2e36c462537
    Signed-off-by: Fatih Degirmenci <fatih.degirmenci@ericsson.com>

diff --git a/docs/submodules/releng b/docs/submodules/releng
index 63fbd31..53ba3fc 160000 (submodule)
--- a/docs/submodules/releng
+++ b/docs/submodules/releng
@@ -1 +1 @@
-Subproject commit 63fbd31ac218846da13f84ee17ef7a61e159055f
+Subproject commit 53ba3fc16aa04a8f8f9a9bcb9dd2da9fc1f27510