Refine custom serialization.

  * MacMapState: Need to read/write instance fields according to
    specification of Java object serialization.
  * No synchronization is needed in readObject() because the instance is
    not yet visible to other instances when readObject() is called.

Change-Id: I8aa1634ad981b4215c6232d277f3f0bd98d52d58
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>
Merge "Refine custom serialization."