Svirt test.

  Fix virsh.start to return CmdResult object
  Fix dummyvirsh.define() to return CmdResultObject.
  Fix libvirt_xml/vm_xml.
  Fix the context_pattern in get_context_from_str method.
  Add attach_disk and dettach_disk in VM class.
  Add test for svirt attach disk.
  libvirt_svirt: Add test for some domain operations.

 libvirt/tests/cfg/svirt/svirt_attach_disk.cfg     |   43 +++++
 libvirt/tests/cfg/svirt/svirt_guest_operation.cfg |   46 ++++++
 libvirt/tests/src/svirt/svirt_attach_disk.py      |   79 +++++++++
 libvirt/tests/src/svirt/svirt_guest_operation.py  |  181 +++++++++++++++++++++
 virttest/libvirt_vm.py                            |   22 ++-
 virttest/libvirt_xml/vm_xml.py                    |   15 +-
 virttest/libvirt_xml_unittest.py                  |    8 +
 virttest/utils_selinux.py                         |    2 +-
 virttest/virsh.py                                 |   12 +-
 9 files changed, 392 insertions(+), 16 deletions(-)
 create mode 100644 libvirt/tests/cfg/svirt/svirt_attach_disk.cfg
 create mode 100644 libvirt/tests/cfg/svirt/svirt_guest_operation.cfg
 create mode 100644 libvirt/tests/src/svirt/svirt_attach_disk.py
 create mode 100644 libvirt/tests/src/svirt/svirt_guest_operation.py