3006 VERIFY[S,U,P] and ASSERT[S,U,P] frequently check if first argument is zero

@@ -897,11 +897,11 @@
         dmu_tx_hold_t *txh;
         spa_t *spa = tx->tx_pool->dp_spa;
         uint64_t memory, asize, fsize, usize;
         uint64_t towrite, tofree, tooverwrite, tounref, tohold, fudge;
 
-        ASSERT3U(tx->tx_txg, ==, 0);
+        ASSERT0(tx->tx_txg);
 
         if (tx->tx_err)
                 return (tx->tx_err);
 
         if (spa_suspended(spa)) {