tests: change main and wallet tests to BOOST_FIXTURE_TEST_SUITE

Avoid this travis error:

    test_bitcoin: chainparams.cpp:330: const CChainParams& Params():
    Assertion `pCurrentParams' failed.
    unknown location(0): fatal error in "subsidy_limit_test": signal:
    SIGABRT (application abort requested)
    test/allocator_tests.cpp(116): last checkpoint

src/test/main_tests.cpp

@@ -5,9 +5,11 @@
 #include "primitives/transaction.h"
 #include "main.h"
 
+#include "test/test_bitcoin.h"
+
 #include <boost/test/unit_test.hpp>
 
-BOOST_AUTO_TEST_SUITE(main_tests)
+BOOST_FIXTURE_TEST_SUITE(main_tests, TestingSetup)
 
 BOOST_AUTO_TEST_CASE(subsidy_limit_test)
 {

src/test/wallet_tests.cpp

@@ -9,6 +9,8 @@
 #include <utility>
 #include <vector>
 
+#include "test/test_bitcoin.h"
+
 #include <boost/foreach.hpp>
 #include <boost/test/unit_test.hpp>
 
@@ -23,7 +25,7 @@ using namespace std;
 
 typedef set<pair<const CWalletTx*,unsigned int> > CoinSet;
 
-BOOST_AUTO_TEST_SUITE(wallet_tests)
+BOOST_FIXTURE_TEST_SUITE(wallet_tests, TestingSetup)
 
 static CWallet wallet;
 static vector<COutput> vCoins;