b2b_entities: remove no-op and improve code clarity

Related to #3011

(cherry picked from commit 4b3ff72)

modules/b2b_entities/dlg.c

@@ -3411,8 +3411,8 @@ void b2b_tm_cback(struct cell *t, b2b_table htable, struct tmcb_params *ps)
 	current_dlg = 0;
 	if(b2be_db_mode == WRITE_THROUGH && dlg_state>B2B_CONFIRMED)
 	{
-		if (b2b_ev == -1 && lock_taken != 1)
-			lock_get(&htable[hash_index].lock);
+		/* the lock is already aquired above, since B2BE_SERIALIZE_STORAGE()
+		 * is true for the WRITE_THROUGH b2be_db_mode */
 
 		for(aux_dlg = htable[hash_index].first; aux_dlg; aux_dlg = aux_dlg->next)
 		{