fix references to Region.DEFAULT, using nil as default region now

aws/core/src/main/clojure/org/jclouds/aws/ebs.clj

@@ -27,6 +27,16 @@
     (org.jclouds.aws.ec2.domain Volume Snapshot AvailabilityZone)
     (org.jclouds.aws.ec2.options DescribeSnapshotsOptions DetachVolumeOptions CreateSnapshotOptions)))
 
+(defn snapshot?
+  "Returns true iff the argument is a org.jclouds.aws.ec2.domain.Snapshot."
+  [s]
+  (instance? Snapshot s))
+
+(defn volume?
+  "Returns true iff the argument is a org.jclouds.aws.ec2.domain.Volume."
+  [v]
+  (instance? Volume v))
+
 (defn #^org.jclouds.aws.ec2.services.ElasticBlockStoreClient
   ebs-service
   "Returns the synchronous ElasticBlockStoreClient associated with
@@ -40,7 +50,8 @@
    keyword or already a Region instance. An optional second argument
    is returned if the first cannot be coerced into a Region.
    Returns nil otherwise."
-  [v & [default-region]]
+  ([v] (get-region v nil))
+  ([v default-region]
     (cond
       (keyword? v) (Region/fromValue (name v))
       (instance? Region v) v
@@ -49,7 +60,7 @@
                                    (Region/fromValue (if (> (.indexOf zone "-") -1)
                                                        (subs zone 0 (-> zone count dec))
                                                        zone)))
-    :else default-region))
+    :else default-region)))
 
 (defn get-volume-id
   "Returns a string volume ID taken from the given string, keyword, or Volume argument."
@@ -70,7 +81,7 @@
   [& [region & volume-ids]]
   (set
     (.describeVolumesInRegion (ebs-service)
-      (get-region region Region/DEFAULT)
+      (get-region region)
       (into-array String (map get-volume-id
                            (if (get-region region)
                              volume-ids
@@ -124,7 +135,7 @@
         options (snapshot-options (dissoc options :region))]
     (set
       (.describeSnapshotsInRegion (ebs-service)
-        (get-region region Region/DEFAULT)
+        (get-region region)
         (into-array DescribeSnapshotsOptions [options])))))
 
 (defn create-snapshot