Fix incorrect readResolve signatures

Fix incorrect readResolve signatures

In several Serializable classes the return type of the readResolve
method is the class. However this is incorrect - the return type must
be Object or it is not recognized by the serialization framework.
Eclipse actually flags the incorrect signature with the "unused" warning
but the warning was suppressed in the code. Using the correct Object
return type, Eclipse doesn't issue the warning.

Change-Id: Id53182925fa48879f1f754c3f25361fb846b23ca
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>