blockbuf_get_writepos, when all existing buffers in blockbuf list are full, a new block buffer is created and added to the list. Adding to the list is done with mutex on hold. Mutex shouldn't be freed before the next iteration in while loop, which expects that bblist mutex is on hold. At the end of the function, removed an unnecessary debug assertion.
testlog.c
Enabled more intensive write test. Replaced TRUE and FALSE with true, false, respectively.
skygw_utils.cc
simple_mutex_unlock, added debug assertion to ensure that pthread mutex's user counter is always at least 0 (it goes negative in double free).
cd507f1461