Update git submodules

* Update docs/submodules/yardstick from branch 'master'
  - Merge "Improve "Libvirt.virsh_destroy_vm" function"
  - Improve "Libvirt.virsh_destroy_vm" function

    Read the command exit code and log a warning in case the VM destroy
    process went wrong.

    JIRA: YARDSTICK-943

    Change-Id: I2750b8d4a8f67af081c1988510cf5aca848a2cf1
    Signed-off-by: Rodolfo Alonso Hernandez <rodolfo.alonso.hernandez@intel.com>

diff --git a/docs/submodules/yardstick b/docs/submodules/yardstick
index 79da68a..9298323 160000 (submodule)
--- a/docs/submodules/yardstick
+++ b/docs/submodules/yardstick
@@ -1 +1 @@
-Subproject commit 79da68a8d4529bbc132228785f0e4c40506fa3ab
+Subproject commit 929832345dab22c99b1fc331902be5509551576e