Update git submodules

Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Merge "Logging: Enhance logging with separate files and timestamps"
  - Logging: Enhance logging with separate files and timestamps

    This patch adds following:
    1. overall.log file is change to vsperf-overall-timestamp.log files
    2. The overall.log files will include timestamps too.
    3. Separate log files for infrastructure metrics.
    4. All timestamps of the logfiles for a given test will be same.
    5. Store the timestamp in 'LOG_TIMESTAMP'
    6. Create metrics-log only if 'COLLECTOR' is set to 'Collectd'

    JIRA: VSPERF-586

    Change-Id: I35d373a66b1074f6ee1a440ffc82bc3db03f36e7
    Signed-off-by: Sridhar K. N. Rao <sridhar.rao@spirent.com>