dpdk: Support dpdk vhost-user client mode

dpdk: Support dpdk vhost-user client mode

Support of vhost-user client mode has been added for both
OVS and VPP. VSPERF configures vhost-user server mode
in vswitches by default for backward compatibility.
Support of vhost-user server mode is deprecated
in OVS and it can be removed in future releases. Once it will
happen, we have to change vsperf default behavior to
usage of vhost-user client ports at vswitch side.

This patch also fixes processing of boolean configuration
parameters passed via --test-params option. In the past
it was not possible to set boolean value to False through
--test-params option.

JIRA: VSPERF-517

Change-Id: I65e341f820edd6c720043a4acc74c5140b05db18
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>