Update git submodules

Update git submodules

* Update docs/submodules/vswitchperf from branch 'master'
  - vpp: Implement missing dump and del functions

    Implementaiton of VPP methods dump_xconnect(), del_xconnect() and
    del_bridge().

    JIRA: VSPERF-576

    Change-Id: Ifb3094d11d1b135e9a33effb1bf6d502db319a30
    Signed-off-by: Martin Klozik <martin.klozik@tieto.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: Richard Elias <richard.elias@tieto.com>