libvirt_bench/dump_with_netperf: fix the wrong method of _is_netperf_running().

The original method to verify that netperf is running in guest is wrong, we can
not see any process named netperf in guest. Instead, this patch check the log file
of autotest.netperf in guest and say that netperf is running in guest.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
libvirt_bench: replace 'autotest' with 'autotest-local'

As autotest script is already removed, now we are using autotest-local
for it.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>