Make sure all url-params are url-encoded

Refs: #3956

kamaki/clients/__init__.py

@@ -357,11 +357,11 @@ class Client(object):
     def set_header(self, name, value, iff=True):
         """Set a header 'name':'value'"""
         if value is not None and iff:
-            self.headers[name] = value
+            self.headers[name] = unicode(value)
 
     def set_param(self, name, value=None, iff=True):
         if iff:
-            self.params[name] = value
+            self.params[name] = unicode(value)
 
     def request(
             self, method, path,