statement rollback issue after 5.1.43 merge

[Seppo Jaakola]

After the 5.1.43, sysbench oltp gives consistency failures with following configuration:

# load balancer choice
load_balancer=multihost

# gcs backend choice
gcs=gcomm

# sysbench configuration
user=root
password=rootpass
host=127.0.0.1
port=3306
users=6
duration=60
requests=0
rows=200
mode=complex
readonly=off

this tetst results in inconsistency in 3 node cluster

[Seppo Jaakola (seppo-jaakola)]

This problme is dues to statement rollbacks, which are not properly handled in wsrep code.
wsrep patch calls wsrep->post_rollback() for both full and stmt rollbacks. However, in stmt rollback case the underlying transaction remains healthy and will commit later. And if post_rollback() was called, the trx has been erased from provider library and wsrep->pre_commit() does not replicate the transaction.