Adds disk_format parameter to upload_volume method in volumes client

Adds a third parameter, disk_format, to the upload_volume method of
the volumes client. The parameter is also added to the Tempest
configuration and defaults to "raw" if not set.

Closes-Bug: #1218666
Change-Id: I6c62796161c9219cbd80eb9fecc7fbb0f3a4681a
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 8d96858..064464b 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -246,6 +246,8 @@
 # Unless you have a custom Keystone service catalog implementation, you
 # probably want to leave this value as "volume"
 catalog_type = volume
+# The disk format to use when copying a volume to image
+disk_format = raw
 # Number of seconds to wait while looping to check the status of a
 # volume that is being made available
 build_interval = 10