libvirt: introduce freeze filesystems

Adds method to freeze in Guest's object which replace direct call to
libvirt.

Implements: blueprint libvirt-clean-driver
Change-Id: Ia530b1072c5af21dc114be627af90a39e38fa01b

nova/tests/unit/virt/libvirt/fakelibvirt.py

@@ -773,6 +773,9 @@ class Domain(object):
     def abortJob(self):
         pass
 
+    def fsFreeze(self):
+        pass
+
 
 class DomainSnapshot(object):
     def __init__(self, name, domain):

nova/tests/unit/virt/libvirt/test_guest.py

@@ -369,6 +369,10 @@ class GuestTestCase(test.NoDBTestCase):
         with mock.patch.object(self.domain, "isActive", return_value=False):
             self.assertFalse(self.guest.is_active())
 
+    def test_freeze_filesystems(self):
+        self.guest.freeze_filesystems()
+        self.domain.fsFreeze.assert_called_once_with()
+
 
 class GuestBlockTestCase(test.NoDBTestCase):
 

nova/virt/libvirt/driver.py

@@ -1520,7 +1520,7 @@ class LibvirtDriver(driver.ComputeDriver):
             # We should be able to remove domain at the end.
             domain = guest._domain
             if quiesced:
-                domain.fsFreeze()
+                guest.freeze_filesystems()
             else:
                 domain.fsThaw()
         except libvirt.libvirtError as ex:

nova/virt/libvirt/guest.py

@@ -369,6 +369,10 @@ class Guest(object):
         "Determines whether guest is currently running."
         return self._domain.isActive()
 
+    def freeze_filesystems(self):
+        """Freeze filesystems within guest."""
+        self._domain.fsFreeze()
+
 
 class BlockDevice(object):
     """Wrapper around block device API"""