Revert "WAL_CHECKSUM_WHOLE: turn off to make sure sver 0 in wal files"

1, sdb designated initialization makes walHead all fields 0;
2, dnodeVWrite: user "t" in SRpcHead makes sver 0;

This reverts commit 24ab0bdf.

src/wal/CMakeLists.txt

 CMAKE_MINIMUM_REQUIRED(VERSION 2.8)
 PROJECT(TDengine)
 
-#ADD_DEFINITIONS(-DWAL_CHECKSUM_WHOLE)
+ADD_DEFINITIONS(-DWAL_CHECKSUM_WHOLE)
 
 INCLUDE_DIRECTORIES(inc)
 AUX_SOURCE_DIRECTORY(${CMAKE_CURRENT_SOURCE_DIR}/src SRC)