hash: fix race condition at creation

hash: fix race condition at creation

To avoid a race condition while creating a new hash object, the
list has to be locked before the lookup, and released only once the
new object is added in the list.

As the lock is held by the rte_ring_create(), move its creation at the
beginning of the function and only take the lock after the ring is
created to avoid a deadlock.

Fixes: 48a3991196 ("hash: replace with cuckoo hash implementation")

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>