Fix '"is" with a literal' syntax warnings

As of Python 3.8, "is" with a literal is a syntax warning and may become
an error in the future. Kazoo ran afoul of this in a few places however.

kazoo/protocol/serialization.py

@@ -111,7 +111,7 @@ def deserialize(cls, bytes, offset):
         password, offset = read_buffer(bytes, offset)
 
         try:
-            read_only = bool_struct.unpack_from(bytes, offset)[0] is 1
+            read_only = bool_struct.unpack_from(bytes, offset)[0] == 1
             offset += bool_struct.size
         except struct.error:
             read_only = False
@@ -446,4 +446,4 @@ def serialize(self):
     def deserialize(cls, bytes, offset):
         t, done, err = multiheader_struct.unpack_from(bytes, offset)
         offset += multiheader_struct.size
-        return cls(t, done is 1, err), offset
+        return cls(t, done == 1, err), offset