Description of problem:
"Clone this disk" button should disable for scsi disk guest in virt-manager GUI

Version-Release number of selected component (if applicable):
virt-manager-1.4.1-1.el7.noarch
virt-manager-common-1.4.1-1.el7.noarch
virt-install-1.4.1-1.el7.noarch
libvirt-3.1.0-2.el7.x86_64
qemu-kvm-rhev-2.8.0-6.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
Testing environment preparation according to Bug 1420190.

1. Installed a guest with disk on scsi pool.
# virsh dumpxml rhel7.2-juzhou
...
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native'/>
      <source dev='/dev/disk/by-path/pci-0000:18:00.1-fc-0x203500a0b85b0acc-lun-0'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </disk>
...

2. Then clone it to rhel7.2-juzhou-clone, which should use volume:  unit:0:0:1 via virt-manager GUI.
2.1 Select guest: rhel7.2-juzhou
2.2 Right click guest: rhel7.2-juzhou
2.3 Select 'Clone' to clone guest.

3. In  "Clone Virtual Machine" page, change Storage to "Clone this disk" then click "Clone".

Actual results:
Failed to clone guest with error:
Error creating virtual machine clone 'rhel7.2-juzhou-clone': missing source information for device vda

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/asyncjob.py", line 88, in cb_wrapper
    callback(asyncjob, *args, **kwargs)
  File "/usr/share/virt-manager/virtManager/clone.py", line 860, in _async_clone
    self.clone_design.start_duplicate(meter)
  File "/usr/share/virt-manager/virtinst/cloner.py", line 482, in start_duplicate
    dom = self.conn.defineXML(self.clone_xml)
  File "/usr/lib64/python2.7/site-packages/libvirt.py", line 3564, in defineXML
    if ret is None:raise libvirtError('virDomainDefineXML() failed', conn=self)
libvirtError: missing source information for device vda

Expected results:
Disable this item if not supported.

Additional info:
I.
I can also reproduce bug issue with guest installed with iscsi pool.

II.
And for glusterfs pool, we'll meet another kind of error:
1. Clone this disk (enable)-> failed
Uncaught error validating input: [Errno 2] No such file or directory: 'gluster://10.66.4.131/gluster-vol1'

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/clone.py", line 821, in finish
    if not self.validate():
  File "/usr/share/virt-manager/virtManager/clone.py", line 800, in validate
    cd.setup_clone()
  File "/usr/share/virt-manager/virtinst/cloner.py", line 437, in setup_clone
    self._setup_disk_clone_destination(orig_disk, clone_disk)
  File "/usr/share/virt-manager/virtinst/cloner.py", line 363, in _setup_disk_clone_destination
    clone_disk.validate()
  File "/usr/share/virt-manager/virtinst/devicedisk.py", line 863, in validate
    self._storage_backend.validate(self)
  File "/usr/share/virt-manager/virtinst/diskbackend.py", line 353, in validate
    err, msg = self.is_size_conflict()
  File "/usr/share/virt-manager/virtinst/diskbackend.py", line 390, in is_size_conflict
    vfs = os.statvfs(os.path.dirname(self._path))
OSError: [Errno 2] No such file or directory: 'gluster://10.66.4.131/gluster-vol1'

2. Customize a path - >failed
Uncaught error validating input: Clone onto existing storage volume is not currently supported: 'gluster://10.66.4.131/gluster-vol1/test-qcow2.img'


As a summary, for pool type doesn't support volume creation should choose 'Share disk with xxx' as default, and disabled other items.