[qa] rpc-tests: Apply random offset to portseed

This helps to skip over resources, which are blocked by regtest bitcoind
zombie nodes

Author: MarcoFalke

qa/pull-tester/rpc-tests.py

@@ -246,14 +246,18 @@ def __init__(self, num_tests_parallel, test_list=None, flags=None):
         self.test_list = test_list
         self.flags = flags
         self.num_running = 0
+        # In case there is a graveyard of zombie bitcoinds, we can apply a
+        # pseudorandom offset to hopefully jump over them.
+        # (625 is PORT_RANGE/MAX_NODES)
+        self.portseed_offset = int(time.time() * 1000) % 625
         self.jobs = []
 
     def get_next(self):
         while self.num_running < self.num_jobs and self.test_list:
             # Add tests
             self.num_running += 1
             t = self.test_list.pop(0)
-            port_seed = ["--portseed=%s" % len(self.test_list)]
+            port_seed = ["--portseed={}".format(len(self.test_list) + self.portseed_offset)]
             log_stdout = tempfile.SpooledTemporaryFile(max_size=2**16)
             log_stderr = tempfile.SpooledTemporaryFile(max_size=2**16)
             self.jobs.append((t,