virttest.qemu_vm: PEP8 fixes

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
virttest.test_setup: PEP8 fixes

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Add readonly mode support for virsh command.

Readonly mode is an important part for virsh command,so add
a boolean parameter 'readonly' when execute virsh commnd.

Signed-off-by: Yanbing Du <ydu@redhat.com>
qemu.test.netperf_udp: Some modify of netperf_udp

This patch modify the method of et netperf, make the script support
UDP_RR test, also modify the temporary dir.

Signed-off-by: Yunping Zheng <yunzheng@redhat.com>