virsh.start: Add virsh_exec to init VirshSession.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Merge pull request #198 from yangdongsheng/start

virsh.start: Add virsh_exec to init VirshSession.
virsh_attach_detach_disk.cfg: Resolve a conflict in options '--mode readonly' and '--shareable'.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Merge pull request #202 from yangdongsheng/at_disk

virsh_attach_detach_disk.cfg: Resolve a conflict in options.
virsh_attach_detach_disk: Add a case to cover ejcet CDROM after attach cdrom

Signed-off-by: Yanbing Du <ydu@redhat.com>
virsh_attach_detach_disk: Support attach|detach disk image format

1. Using qemu_storage.QemuImg to create disk image, which can specified
the image format.
2. Add a sub-case to test qcow2 disk image attach|detach.

Signed-off-by: Yanbing Du <ydu@redhat.com>
virsh_attach_detach_disk: Add a negative case to test IDE disk hotplug

Signed-off-by: Yanbing Du <ydu@redhat.com>
virsh_attach_detach_disk: Add a case to attach logical volume

Signed-off-by: Yanbing Du <ydu@redhat.com>