Description of problem:
I'm using oVirt 3.6.7 now. I want to enable tunnel migration feature. 
But when i set tunnel_migration value of vm as Ture through python
SDK(I can't find any place to enable tunnel migration on the web ui,
so i use SDK), then migrate the vm i got the following error message:
 
Thread-9417628::ERROR::2017-03-07 11:25:48,538::migration::310::virt.vm::(run) vmId=`08b4ccc1-c508-439b-a9ba-ca0d42a7072c`::Failed to migrate
Traceback (most recent call last):
  File "/usr/share/vdsm/virt/migration.py", line 298, in run
    self._startUnderlyingMigration(time.time())
  File "/usr/share/vdsm/virt/migration.py", line 364, in _startUnderlyingMigration
    self._perform_migration(duri, muri)
  File "/usr/share/vdsm/virt/migration.py", line 403, in _perform_migration
    self._vm._dom.migrateToURI3(duri, params, flags)
  File "/usr/share/vdsm/virt/virdomain.py", line 68, in f
    ret = attr(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/vdsm/libvirtconnection.py", line 124, in wrapper
    ret = f(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/vdsm/utils.py", line 1313, in wrapper
    return func(inst, *args, **kwargs)
  File "/usr/lib64/python2.7/site-packages/libvirt.py", line 1836, in migrateToURI3
    if ret == -1: raise libvirtError ('virDomainMigrateToURI3() failed', dom=self)
libvirtError: argument unsupported：migration URI is not supported by tunnelled migration

Version-Release number of selected component (if applicable):
OS: RHEL7.2
Libvirt: 1.2.17-13.el7_2.5
Qemu-kvm-ev: 2.3.0-31.el7_2.23
ovirt-engine: 3.6.7.5
vdsm: 4.17.32-2

How reproducible:
always

Steps to Reproduce:
1.use python sdk set the tunnel_migration property of vm as True
2.migrate the vm

Actual results:
vm migration failed

Expected results:
vm migration succeeded

Additional info:
I can't find any place to enable tunneled migration on the Web UI. What's the status of this feature?