test and refactor
Merge pull request #30 from fengjingchao/inst

test and refactor
remove needcmdsinreply and add test for nilstatus preparing handle reply
complete nil status handle prepare reply
finish handle prepare reply at preaccepted recovery
Merge pull request #31 from fengjingchao/inst

remove needcmdsinreply and add test for nilstatus preparing handle reply
add check before increment counts and add test for preaccept ok
Merge pull request #32 from fengjingchao/inst

add check before increment counts and add test for preaccept ok
bug fixes on seq update.
bug fix on Union and test on fast path
fix panic cases
fix preaccept-ok/-reply
add notAbleToFastPath