Update git submodules

* Update docs/submodules/bottlenecks from branch 'stable/danube'
  - Add docker clean-up for run test

    JIRA: BOTTLENECK-148

    Currently, only OPNFV CI includes env-cleanup for Bottlenecks.
    It is preferable to also include the operation locally
    for test automation and repeatability.

    Changes:
    1. Translate tab into 4 spaces

    Change-Id: I9f4efb95c155e442afd3141c00f707421c61b2da
    Signed-off-by: yuyang <Gabriel.yuyang@huawei.com>
    (cherry picked from commit fe83578bd2fe1a09f8334f85e30a0afbb68cc5cc)

diff --git a/docs/submodules/bottlenecks b/docs/submodules/bottlenecks
index 0d41307..72d75db 160000 (submodule)
--- a/docs/submodules/bottlenecks
+++ b/docs/submodules/bottlenecks
@@ -1 +1 @@
-Subproject commit 0d41307d670de19f1a27cda743bbac4d87367d0c
+Subproject commit 72d75db77faa31a1c116e7856e1487511a37a807