[qa] Sort scripts by time for pull_tester and don't overwrite setup_chain

qa/rpc-tests/segwit.py

@@ -71,9 +71,10 @@ def getutxo(txid):
 
 class SegWitTest(BitcoinTestFramework):
 
-    def setup_chain(self):
-        print("Initializing test directory "+self.options.tmpdir)
-        initialize_chain_clean(self.options.tmpdir, 3)
+    def __init__(self):
+        super().__init__()
+        self.setup_clean_chain = True
+        self.num_nodes = 3
 
     def setup_network(self):
         self.nodes = []