ci: Decrease hugepages size for VERIFY&MERGE jobs

ci: Decrease hugepages size for VERIFY&MERGE jobs

VSPERF by default requires allocation of hugepages with total
size of 10GB. However for MERGE and VERIFY jobs less memory is
required and default size of 10GB can cause issues. Thus amount
of memory was limited and other minor enhancements were introduced:
* sysstat system package is installed at nodes running VERIFY
  and MERGE jobs
* WHITELIST_NICS was set to empty list by default to avoid
  automatic bind of NICs to DPDK. Old default value could
  cut off network connection to DUT.
* imports were fixed at both integration.py and testcase.py

JIRA: VSPERF-391

Change-Id: Ic07d68f4591ae697c1b8edeae6c0cffe47c065ce
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: Bill Michalowski <bmichalo@redhat.com>
Reviewed-by: Antonio Fischetti <antonio.fischetti@intel.com>