os/newstore: fix deadlock when newstore_sync_transaction=true

os/newstore: fix deadlock when newstore_sync_transaction=true

There is a deadlock issue in Newstore when newstore_sync_transaction = true.
With sync_transaction to true, the txc state machine will go all the way down
from STATE_IO_DONE to STATE_FINISHING in the same thread, while holding the osr->qlock().
The deadlock is caused in _txc_finish and _osr_reap_done, when trying to
lock osr->qlock again.

Since the _txc_finish can be called with(in sync transaction mode) or without
(in async transaction mode) holding the qlock, so fix this by setting the qlock
to PTHREAD_MUTEX_RECURSIVE, thus we can recursive acquire the qlock.

Signed-off-by: Xiaoxi Chen <xiaoxi.chen@intel.com>