Test case is starting too many servers that are not really
needed for original problem testing. This fix reduces
number of servers to make test case smaller and more
robust.
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>
Found two bugs
(1) have_committing_connections was missing mutex unlock on one
exit case. As this function is called on a loop it caused mutex
lock when we already owned the mutex. This could cause hang.
(2) wsrep_RSU_begin did set up error code when partition to
be dropped could not be MDL-locked because of concurrent
operations but wrong error code was propagated to upper layer
causing error to be ignored. This could have also caused
the hang.
