Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "restore Heat stack failure logs for CI"
  - restore Heat stack failure logs for CI

    We need to see what Heat failures occured
    so that we can debug CI failures.

    The only way to do this seems to be to use the
    private event_utils.get_events function to
    query for all failures

    Also since we had a failure go ahead and dump the
    Heat template that failed.

    Sample output:

    2018-03-25 23:50:08,765 [INFO] yardstick.orchestrator.heat heat.py:629 Creating stack 'yardstick-460ed969' START
    2018-03-25 23:50:21,932 [ERROR] yardstick.orchestrator.heat heat.py:644 Resource CREATE failed: BadRequest: resources.yardstick-460ed969-xe1: Invalid input for operation: physical_network 'nosuch' unknown for flat provider network.
    Neutron server returns request_ids: ['req-6f981f1e-a9e2-4114-af84-1ee528aed51b']
    2018-03-25 23:50:21,933 [ERROR] yardstick.orchestrator.heat heat.py:644 BadRequest: resources.yardstick-460ed969-xe1: Invalid input for operation: physical_network 'nosuch' unknown for flat provider network.
    Neutron server returns request_ids: ['req-6f981f1e-a9e2-4114-af84-1ee528aed51b']
    2018-03-25 23:50:21,972 [ERROR] yardstick.orchestrator.heat heat.py:645 {'description': '\n'
                    'All referred generated resources are prefixed with the '
                    'template\n'
                    'name (i.e. yardstick-460ed969).\n',
     'heat_template_version': '2013-05-23',
     'outputs': {'trafficgen_1.yardstick-460ed969': {'description': 'VM UUID',
                                                     'value': {'get_resource': 'trafficgen_1.yardstick-460ed969'}},
                 'trafficgen_1.yardstick-460ed969-fip': {'description': 'floating '
                                                                        'ip '
    JIRA: YARDSTICK-998

    Change-Id: Ia8f4e5ba7e280fb9086519680d5ee90a2b442e6b
    Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 5293564..c6a42e5 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 5293564955b96ff3973f498b1f526e70e792b12b
+Subproject commit c6a42e58668389e70320601565eb0a677f1105cd