vmem: do not reinitialize the pool[0]->chunks_mtx mutex

The pool[0]->chunks_mtx mutex is locked at chunk.c:178
(called from malloc_init_base_pool() at jemalloc.c:362)
before being initialized at chunk.c:415
(called from malloc_init_base_pool() at jemalloc.c:364).

Move a call to pools_shared_data_create() to pool_new()
after a call to chunk_boot() in order to fix this bug.

Ref: pmem/issues#17
blk: fix return value of BTT nsmap callback

Ref: pmem/issues#18
vmem: fix race condition between library constructors

Some applications need to create pool in constructor
called before constructor from vmem.
Merge pull request #71 from plebioda/fix-btt-nsmap-return-value

blk: fix return value of BTT nsmap callback
Merge pull request #74 from ldorau/vmem-do-not-reinitialize-pool-chunks_mtx-mutex

vmem: do not reinitialize the pool[0]->chunks_mtx mutex
Merge pull request #75 from spawlows/vmem-constructors-race

vmem: fix race condition between library constructors
vmem: add the malloc_rwlock_t type
vmem: change type of pool->arenas_lock to malloc_rwlock_t
vmem: fix race condition in je_mallocx()

Ref: pmem/issues#15