test: Remove UNITTEST params

UNITTEST parameter are not used by any current tests, and the model
(modifyable parameters) is inconvenient when unit-testing. As
they are stored in a global structure eevery test
would have to (re)set up its own parameters.

For consistency it is also better to test with MAIN parameters.

src/test/test_bitcoin.cpp

@@ -29,7 +29,7 @@ extern void noui_connect();
 TestingSetup::TestingSetup()
 {
         fPrintToDebugLog = false; // don't want to write to debug.log file
-        SelectParams(CBaseChainParams::UNITTEST);
+        SelectParams(CBaseChainParams::MAIN);
         noui_connect();
 #ifdef ENABLE_WALLET
         bitdb.MakeMock();