Update git submodules

Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - Merge "trex: Support of SCAPY frame definition"
  - trex: Support of SCAPY frame definition

    T-Rex implementation in vsperf was improved to support:

    * SCAPY frame definition, so additional network protocols
      can be generated by T-Rex and sent towards DUT
    * VLAN configuration defined by TRAFFIC['vlan']
    * enable or disable L2, L3, L4 and VLAN protocols
      as configured by TRAFFIC dictionary

    VSPERF documentation was updated with examples of SCAPY
    frame definition usage.

    JIRA: VSPERF-565

    Change-Id: Iff9baba47a1e83d321f6ba3c1c482965b9882241
    Signed-off-by: Martin Klozik <martinx.klozik@intel.com>
    Reviewed-by: Al Morton <acmorton@att.com>
    Reviewed-by: Christian Trautman <ctrautma@redhat.com>
    Reviewed-by: Sridhar Rao <sridhar.rao@spirent.com>
    Reviewed-by: Trevor Cooper <trevor.cooper@intel.com>
    Reviewed-by: Richard Elias <richardx.elias@intel.com>