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/rpc_createmultisig.py

@@ -28,8 +28,6 @@ class RpcCreateMultiSigTest(BitcoinTestFramework):
         self.setup_clean_chain = True
         self.num_nodes = 3
         self.supports_cli = False
-        if self.is_bdb_compiled():
-            self.requires_wallet = True
 
     def get_keys(self):
         self.pub = []
@@ -50,6 +48,7 @@ class RpcCreateMultiSigTest(BitcoinTestFramework):
         self.wallet = MiniWallet(test_node=node0)
 
         if self.is_bdb_compiled():
+            self.import_deterministic_coinbase_privkeys()
             self.check_addmultisigaddress_errors()
 
         self.log.info('Generating blocks ...')