Update git submodules

Update git submodules

* Update docs/submodules/vswitchperf from branch 'stable/euphrates'
  - trex_prom: Add promiscuous option for trex for SRIOV tests

    Adds option to enable promiscuous mode for Trex traffic
    generator to allow for SR-IOV tests to work correctly.
    Trex by default only accepts packets based on destination
    MAC address matching what is configured on server in
    /etc/trex-cfg.yaml. This removes that limitation since
    SR-IOV tests require mac addresses to be modified in the
    generated packets to correctly route packets to the relevant
    VFs.

    JIRA: VSPERF-531

    Change-Id: I19b64f364c8a1b656994c82c96f47a68b92486d8
    Signed-off-by: Christian Trautman <ctrautma@redhat.com>
    (cherry picked from commit 5d08ffdf317d31361a528bf1b6d33cd4d0007600)