Update git submodules
* Update docs/submodules/yardstick from branch 'master'
- Merge "bugfix: kill process do not accurately kill "nova-api""
- bugfix: kill process do not accurately kill "nova-api"
JIRA: YARDSTICK-849
1. update the kill process RegEx pattern to be more accurate
2. make attack_process to be parameter so it can be customized if
the SUT is using a different name of attack_process
Change-Id: I569730ced6c24aafbffcf2fc5752d3560d0adac5
Signed-off-by: rexlee8776 <limingjiang@huawei.com>