virt.test: fix some netperf issues

this patch:
1.fix the issue netperf cannot login with two nics,
2.add  netperf test support tcp_crr protocol
3.add an automated way to get the cdrom drive number.
4.modify the file path of netperf.tar.gz. now should
put the src file under "virt/shared/deps"
5.add more step info
qemu.tests: Add stop continue with file copy case

Add a background process to copy file while do stop and continue.
Check the md5 value for the files.

changes from v1:
  - remove the blanks

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
Acked-by: Feng Yang <fyang@redhat.com>
virt.tests.stop_continue: Update test steps

This patch also update its config file, adding
quote mark for some parameters.

Signed-off-by: Qingtang Zhou <qzhou@redhat.com>
Acked-by: Yiqiao Pu <ypu@redhat.com>