use WalletContext scheduler for walletpassphrase callback

test/functional/wallet_keypool.py

@@ -4,7 +4,6 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test the wallet keypool and interaction with wallet encryption/locking."""
 
-import time
 from decimal import Decimal
 
 from test_framework.test_framework import BitcoinTestFramework
@@ -127,8 +126,10 @@ class KeyPoolTest(BitcoinTestFramework):
         nodes[0].keypoolrefill(3)
 
         # test walletpassphrase timeout
-        time.sleep(1.1)
-        assert_equal(nodes[0].getwalletinfo()["unlocked_until"], 0)
+        # CScheduler relies on condition_variable::wait_until() which does not
+        # guarantee accurate timing. We'll wait up to 5 seconds to execute a 1
+        # second scheduled event.
+        nodes[0].wait_until(lambda: nodes[0].getwalletinfo()["unlocked_until"] == 0, timeout=5)
 
         # drain the keypool
         for _ in range(3):