[qa] walletbackup: Sync blocks inside the loop

qa/rpc-tests/walletbackup.py

@@ -45,12 +45,12 @@ class WalletBackupTest(BitcoinTestFramework):
         super().__init__()
         self.setup_clean_chain = True
         self.num_nodes = 4
+        # nodes 1, 2,3 are spenders, let's give them a keypool=100
+        self.extra_args = [["-keypool=100"], ["-keypool=100"], ["-keypool=100"], []]
 
     # This mirrors how the network was setup in the bash test
     def setup_network(self, split=False):
-        # nodes 1, 2,3 are spenders, let's give them a keypool=100
-        extra_args = [["-keypool=100"], ["-keypool=100"], ["-keypool=100"], []]
-        self.nodes = start_nodes(self.num_nodes, self.options.tmpdir, extra_args)
+        self.nodes = start_nodes(self.num_nodes, self.options.tmpdir, self.extra_args)
         connect_nodes(self.nodes[0], 3)
         connect_nodes(self.nodes[1], 3)
         connect_nodes(self.nodes[2], 3)
@@ -79,6 +79,7 @@ class WalletBackupTest(BitcoinTestFramework):
         # Must sync mempools before mining.
         sync_mempools(self.nodes)
         self.nodes[3].generate(1)
+        sync_blocks(self.nodes)
 
     # As above, this mirrors the original bash test.
     def start_three(self):