Protect against missing fields in rackspace endpoint documents

In a specific case a rackspace api endpoint returned no region key

'{"tenantId"=>"654557", "publicURL"=>"https://backup.api.rackspacecloud.com/v1.0/654557"}'

As a guard against this case, this commit sets the region to be global
should it not be defined in the endpoint hash

lib/fog/rackspace/models/identity/service_catalog.rb

@@ -70,7 +70,8 @@ module Fog
         def endpoints_from_array(endpoints)
           hash = {}
           endpoints.each do |endpoint|
-            region = endpoint["region"].downcase.to_sym
+            region_name = endpoint["region"]
+            region = region_name ? region_name.downcase.to_sym : :global
             url = endpoint["publicURL"].freeze
             hash[region] = url
           end
@@ -80,4 +81,4 @@ module Fog
       end
     end
   end
-end
+end