Merge bitcoin/bitcoin#27066: test: Fix intermittent sync issue in wallet_pruning

fa6f67837b test: Fix intermittent sync issue in wallet_pruning (721217.xyz)

Pull request description:

  Setting the mocktime on each loop iteration will make net processing racy and cause a disconnect due to timeout.

  Fix that by setting the mocktime only once.

  Fixes https://github.com/bitcoin/bitcoin/issues/27065

ACKs for top commit:
  brunoerg:
    crACK fa6f67837b

Tree-SHA512: 128b962c05a6fa3caf3ce392e870fff6609ce2206a43bbae6661ecb45291df93bed77fe362a514d4472056f83fb6631df39a5170fa34e41a7577b9685dd26b1f

test/functional/wallet_pruning.py

@@ -39,11 +39,15 @@ class WalletPruningTest(BitcoinTestFramework):
 
     def mine_large_blocks(self, node, n):
         # Get the block parameters for the first block
-        best_block = node.getblock(node.getbestblockhash())
+        best_block = node.getblockheader(node.getbestblockhash())
         height = int(best_block["height"]) + 1
         self.nTime = max(self.nTime, int(best_block["time"])) + 1
         previousblockhash = int(best_block["hash"], 16)
         big_script = CScript([OP_RETURN] + [OP_TRUE] * 950000)
+        # Set mocktime to accept all future blocks
+        for i in self.nodes:
+            if i.running:
+                i.setmocktime(self.nTime + 600 * n)
         for _ in range(n):
             block = create_block(hashprev=previousblockhash, ntime=self.nTime, coinbase=create_coinbase(height, script_pubkey=big_script))
             block.solve()
@@ -57,9 +61,6 @@ class WalletPruningTest(BitcoinTestFramework):
             # Simulate 10 minutes of work time per block
             # Important for matching a timestamp with a block +- some window
             self.nTime += 600
-            for n in self.nodes:
-                if n.running:
-                    n.setmocktime(self.nTime) # Update node's time to accept future blocks
         self.sync_all()
 
     def test_wallet_import_pruned(self, wallet_name):