[ibm] Nullable formats for attributes that may not be returned

tests/ibm/requests/compute/address_tests.rb

@@ -8,7 +8,9 @@ Shindo.tests('Fog::Compute[:ibm] | address requests', ['ibm']) do
     "id"        => String,
     "mode"      => Integer,
     "hostname"  => String,
-    "type"      => Integer
+    "type"      => Integer,
+    "instanceId" => Fog::Nullable::String,
+    "vlan"      => Fog::Nullable::String,
   }
 
   # create_address doesn't return mode, hostname or type attributes

tests/ibm/requests/compute/image_tests.rb

@@ -5,7 +5,7 @@ Shindo.tests('Fog::Compute[:ibm] | image requests', ['ibm']) do
     'visibility'    => String,
     'platform'      => String,
     'owner'         => String,
-    'architecture'  => String,
+    'architecture'  => Fog::Nullable::String,
     'createdTime'   => Integer,
     'location'      => String,
     'productCodes'  => Array,
@@ -13,8 +13,8 @@ Shindo.tests('Fog::Compute[:ibm] | image requests', ['ibm']) do
     'id'            => String,
     'description'   => String,
     'supportedInstanceTypes'  => Array,
-    'manifest'      => String,
-    'documentation' => String
+    'manifest'      => Fog::Nullable::String,
+    'documentation' => Fog::Nullable::String,
   }
 
   # TODO: Actually check this format

tests/ibm/requests/compute/instance_tests.rb

@@ -14,16 +14,18 @@ Shindo.tests('Fog::Compute[:ibm] | instance requests', ['ibm']) do
     'imageId'       => String,
     'launchTime'    => Integer,
     'id'            => String,
+    'ip'            => Fog::Nullable::String,
     'volumes'       => Array,
-    'root-only'     => String,
+    'root-only'     => Fog::Nullable::String,
     'instanceType'  => String,
-    'diskSize'      => String,
+    'diskSize'      => Fog::Nullable::String,
     'requestName'   => String,
     'secondaryIP'   => Array,
     'status'        => Integer,
     'software'      => Array,
     'expirationTime'=> Integer,
-    'owner'         => String
+    'owner'         => String,
+    'vlan'         => Fog::Nullable::String,
   }
 
   @instances_format = {