Add is_incremental to ListVolumeBackup

It's of interest which backups are incremental or full. Returning this
information as a column to the list of backups.

Change-Id: I766330228634d5db678df11c23877077a3635372

openstackclient/tests/unit/volume/v2/fakes.py

@@ -520,6 +520,7 @@ def create_one_backup(attrs=None):
         "object_count": None,
         "container": 'container-' + uuid.uuid4().hex,
         "size": random.randint(1, 20),
+        "is_incremental": False,
         "status": "error",
         "availability_zone": 'zone' + uuid.uuid4().hex,
     }

openstackclient/tests/unit/volume/v2/test_volume_backup.py

@@ -356,6 +356,7 @@ class TestBackupList(TestBackup):
         'Description',
         'Status',
         'Size',
+        'Incremental',
     )
     columns_long = columns + (
         'Availability Zone',
@@ -372,6 +373,7 @@ class TestBackupList(TestBackup):
                 b.description,
                 b.status,
                 b.size,
+                b.is_incremental,
             )
         )
     data_long = []
@@ -383,6 +385,7 @@ class TestBackupList(TestBackup):
                 b.description,
                 b.status,
                 b.size,
+                b.is_incremental,
                 b.availability_zone,
                 volume_backup.VolumeIdColumn(b.volume_id),
                 b.container,

openstackclient/volume/v2/volume_backup.py

@@ -309,8 +309,22 @@ class ListVolumeBackup(command.Lister):
     def take_action(self, parsed_args):
         volume_client = self.app.client_manager.sdk_connection.volume
 
-        columns = ('id', 'name', 'description', 'status', 'size')
+        columns = (
-        column_headers = ('ID', 'Name', 'Description', 'Status', 'Size')
+            'id',
+            'name',
+            'description',
+            'status',
+            'size',
+            'is_incremental',
+        )
+        column_headers = (
+            'ID',
+            'Name',
+            'Description',
+            'Status',
+            'Size',
+            'Incremental',
+        )
         if parsed_args.long:
             columns += ('availability_zone', 'volume_id', 'container')
             column_headers += ('Availability Zone', 'Volume', 'Container')