Adds tests to cover Swift's crossdomain middleware

It adds one test for now, a single unidentified GET call to
"/crossdomain.xml" and compares the response's body to the expected XML
file.

The test can be disabled if marked explicitely as such in the
tempest.conf file

Change-Id: Id88e9da59288f118a605bf20769378190aabdeca
diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 87bf758..7c3371b 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -301,11 +301,13 @@
 # Set operator role for tests that require creating a container
 operator_role = Member
 
-[object-feature-enabled]
+[object-storage-feature-enabled]
 # Set to True if the Account Quota middleware is enabled
 accounts_quotas = True
 # Set to True if the Container Quota middleware is enabled
 container_quotas = True
+# Set to True if the Crossdomain middleware is enabled
+crossdomain_available = True
 
 [boto]
 # This section contains configuration options used when executing tests