hash: add local variable

hash: add local variable

The current implmentation of the hash table is not thread-safe.
This design leads to a segfault when VPP handling a lot of tunnels for
Wireguard, where one thread modify the hash table and other threads
starting to lookup at the same time.

The fix add a local variable to store how many bits are used by a user
object.

Type: fix
Signed-off-by: Gabriel Oginski <gabrielx.oginski@intel.com>
Change-Id: Iecf6b3ef9f308b61015c66277cc459a6d019c9c1