libvirt-test: Add test cases for nodedev-list

Test command: nodedev-list [--tree] [--cap <string>]

1) Run nodedev-list command and check return code.
2) If `cap_option == one`, results are also compared
   with devices get from sysfs.

Signed-off-by: Hao Liu <hliu@redhat.com>
libvirt: Fix nodedev_list in nodedev_create_destroy

1) Change nodedev_list according to change of API in virsh.py.
   There are two references of old nodedev_list API, one is fixed
   in this commit, and another used in nodedev_reset is no need to
   fix.

2) We don't need to start VM when testing host node devices. this
   will save us a little time.

Signed-off-by: Hao Liu <hliu@redhat.com>
libvirt: Fix nodedev_list in pci_passthrough

1) Change nodedev_list according to change of API in virsh.py.

Signed-off-by: Hao Liu <hliu@redhat.com>
Merge pull request #40 from Hao-Liu/nodedev_list

libvirt-test: Add test cases for nodedev-list