Fix ListCoins test failure due to unset g_address_type, g_change_type

New global variables were introduced in bitcoin#11403 and not setting them causes:

    test_bitcoin: wallet/wallet.cpp:4199: CTxDestination GetDestinationForKey(const CPubKey&, OutputType): Assertion `false' failed.
    unknown location(0): fatal error in "ListCoins": signal: SIGABRT (application abort requested)

It's possible to reproduce the failure reliably by running:

    src/test/test_bitcoin --log_level=test_suite --run_test=wallet_tests/ListCoins

Failures happen nondeterministically because boost test framework doesn't run
tests in a specified order, and tests that run previously can set the global
variables and mask the bug.

src/wallet/test/wallet_tests.cpp

@@ -602,6 +602,8 @@ class ListCoinsTestingSetup : public TestChain100Setup
     {
         CreateAndProcessBlock({}, GetScriptForRawPubKey(coinbaseKey.GetPubKey()));
         ::bitdb.MakeMock();
+        g_address_type = OUTPUT_TYPE_DEFAULT;
+        g_change_type = OUTPUT_TYPE_DEFAULT;
         wallet.reset(new CWallet(std::unique_ptr<CWalletDBWrapper>(new CWalletDBWrapper(&bitdb, "wallet_test.dat"))));
         bool firstRun;
         wallet->LoadWallet(firstRun);