Increase swift upload threads to 10

We previously used swiftclient to upload image objects, and it uses
10 threads to upload SLO segments in parallel.  Openstacksdk uses 5
by default.  Increase it to 10 to match swiftclient.  This should
improve our initial upload performance.

Change-Id: Idfee3cbbc9d49d9e14ad7d9db3ceafbd8ca526f6

roles/image-upload-swift/library/image_upload_swift.py

@@ -15,6 +15,7 @@
 # under the License.
 
 import argparse
+import concurrent.futures
 import datetime
 import logging
 import os
@@ -33,7 +34,11 @@ SEGMENT_SIZE = 500000000  # 500MB
 def get_cloud(cloud):
     if isinstance(cloud, dict):
         config = openstack.config.loader.OpenStackConfig().get_one(**cloud)
-        return openstack.connection.Connection(config=config)
+        return openstack.connection.Connection(
+            config=config,
+            pool_executor=concurrent.futures.ThreadPoolExecutor(
+                max_workers=10
+            ))
     else:
         return openstack.connect(cloud=cloud)