test: Make requires_wallet private

The bool is only used to call a public helper, which some tests already
do. So use the public helper in all tests consistently and make the
confusingly named bool private.

test/functional/mempool_unbroadcast.py

@@ -17,8 +17,6 @@ MAX_INITIAL_BROADCAST_DELAY = 15 * 60 # 15 minutes in seconds
 class MempoolUnbroadcastTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
-        if self.is_wallet_compiled():
-            self.requires_wallet = True
 
     def run_test(self):
         self.wallet = MiniWallet(self.nodes[0])
@@ -35,6 +33,7 @@ class MempoolUnbroadcastTest(BitcoinTestFramework):
         self.log.info("Generate transactions that only node 0 knows about")
 
         if self.is_wallet_compiled():
+            self.import_deterministic_coinbase_privkeys()
             # generate a wallet txn
             addr = node.getnewaddress()
             wallet_tx_hsh = node.sendtoaddress(addr, 0.0001)