Cleanup phonon activation in functional tests

Summary:
Some phonon activation logic is left in abc-miner-fund to ensure
we do not break this logic.  Trying to clean up that logic further would
end up scrapping large parts of that test.

Test Plan:
```
test_runner.py abc-miner-fund
test_runner.py mempool_packages
```

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D6796

test/functional/bchn-no-miner-fund-activation.py

@@ -34,8 +34,6 @@
 class MinerFundTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
-        self.extra_args = [
-            ["-phononactivationtime={}".format(PHONON_ACTIVATION_TIME)]]
 
     def check_bip9_state(self, name, status):
         assert_equal(False, 'softforks' in self.nodes[0].getblockchaininfo())
@@ -113,8 +111,13 @@ def run_miner_fund_test(self, bit, name, fund_address):
         version = VERSION_BASE | (1 << bit)
 
         self.stop_node(0)
+<<<<<<< HEAD:test/functional/bchn-no-miner-fund-activation.py
         self.start_node(0,
                         ["-blockversion={}".format(version), "-phononactivationtime={}".format(PHONON_ACTIVATION_TIME)])
+=======
+        self.start_node(
+            0, ['-enableminerfund', "-blockversion={}".format(version)])
+>>>>>>> 9bbe4cd78... Cleanup phonon activation in functional tests:test/functional/abc-miner-fund.py
 
         node = self.nodes[0]
         node.setmocktime(1580000000)

test/functional/mempool_packages.py

@@ -16,23 +16,14 @@
     sync_mempools,
 )
 
-# TODO: The activation code can be reverted after the new policy becomes
-# active.
-
-# Phonon dummy activation time
-ACTIVATION_TIME = 2000000000
-
 MAX_ANCESTORS = 50
 MAX_DESCENDANTS = 50
 
 
 class MempoolPackagesTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
-
-        common_params = ["-maxorphantx=1000",
-                         "-phononactivationtime={}".format(ACTIVATION_TIME)]
-
+        common_params = ["-maxorphantx=1000"]
         self.extra_args = [common_params,
                            common_params + ["-limitancestorcount=5"]]
 
@@ -57,8 +48,6 @@ def chain_transaction(self, node, parent_txid, vout,
         return (txid, send_value)
 
     def run_test(self):
-        [n.setmocktime(ACTIVATION_TIME) for n in self.nodes]
-
         # Mine some blocks and have them mature.
         self.nodes[0].generate(101)
         utxo = self.nodes[0].listunspent(10)