Merge #16420: QA: Fix race condition in wallet_encryption test

024ecd7 QA: Fix race condition in wallet_encryption test (Jonas Schnelli)

Pull request description:

  There is some imprecision probably in the internal HTTPRPCTimer class (haven't exactly figured out where).
  But we can't expect that waiting excatly 2 seconds right after calling `walletpassphrase(2)` will result in a locked wallet due to the nature how we internally handle threads/timers.

  The wallet_encryption test fails regularely in CIs.

  Here is a logged session:
  ```shell
  �[0;34m node0 2019-07-18T18:51:22.569739Z [] ThreadRPCServer method=walletpassphrase user=__cookie__ �[0m
  �[0;34m node0 2019-07-18T18:51:22.628656Z [] queue run of timer lockwallet() in 2 seconds (using HTTP) �[0m
  �[0;34m node0 2019-07-18T18:51:22.629002Z [] Received a POST request for / from 127.0.0.1:46898 �[0m
  �[0;34m node0 2019-07-18T18:51:22.629081Z [] ThreadRPCServer method=dumpprivkey user=__cookie__ �[0m
  �[0;34m node0 2019-07-18T18:51:24.445620Z [] Flushing wallet.dat �[0m
  �[0;34m node0 2019-07-18T18:51:24.451421Z [] Flushed wallet.dat 6ms �[0m
  �[0;34m node0 2019-07-18T18:51:24.631703Z [] Received a POST request for / from 127.0.0.1:46898 �[0m
  �[0;34m node0 2019-07-18T18:51:24.631737Z [] ThreadRPCServer method=dumpprivkey user=__cookie__ �[0m
  �[0;36m test  2019-07-18T18:51:24.632000Z TestFramework (ERROR): Assertion failed �[0m
  �[0;36m                                   Traceback (most recent call last):�[0m
  �[0;36m                                     File "/home/ubuntu/src/test/functional/test_framework/test_framework.py", line 193, in main�[0m
  �[0;36m                                       self.run_test()�[0m
  �[0;36m                                     File "/home/ubuntu/src/test/functional/wallet_encryption.py", line 53, in run_test�[0m
  �[0;36m                                       assert_raises_rpc_error(-13, "Please enter the wallet passphrase with walletpassphrase first", self.nodes[0].dumpprivkey, address)�[0m
  ```

ACKs for top commit:
  promag:
    ACK 024ecd7, simple fix, one second shouldn't hurt.
  MarcoFalke:
    ACK 024ecd7
  fanquake:
    ACK 024ecd7

Tree-SHA512: 0cda1b8969b084bb765d2b35e90a8611c565ee458a7be1f2dde675f8ddbd9b9e421514547a7683f836e2c996e0538eb66b8c5b935b5a81e9319fb2be27624374

Author: fanquake

test/functional/wallet_encryption.py

@@ -49,7 +49,7 @@ def run_test(self):
         assert_equal(privkey, self.nodes[0].dumpprivkey(address))
 
         # Check that the timeout is right
-        time.sleep(2)
+        time.sleep(3)
         assert_raises_rpc_error(-13, "Please enter the wallet passphrase with walletpassphrase first", self.nodes[0].dumpprivkey, address)
 
         # Test wrong passphrase