CI: terminate hanging vsperf before its execution

CI: terminate hanging vsperf before its execution

In case that vsperf terminates unexpectedly, then vsperf itself
or any of executed applications might remain active. It is essential
to terminate any hanging instance of vsperf, ovs, qemu, etc.
before re-execution of vsperf itself. Otherwise vsperf will fail
again.

Change-Id: Idd65288a5171d19fcbfb907a156347eb4b645a88
JIRA: VSPERF-155
Signed-off-by: Martin Klozik <martinx.klozik@intel.com>
Reviewed-by: Maryam Tahhan <maryam.tahhan@intel.com>
Reviewed-by: Al Morton <acmorton@att.com>
Reviewed-by: Brian Castelli <brian.castelli@spirent.com>
Reviewed-by: Gurpreet Singh <gurpreet.singh@spirent.com>
Reviewed-by: Tv Rao <tv.rao@freescale.com>