Make qt test compatible with TestChain100Setup framework

Reset global state after rpc tests, and remove unnecessary ECC initialization
to prevent assert error if it is initialized twice.

src/qt/test/rpcnestedtests.cpp

@@ -148,9 +148,13 @@ void RPCNestedTests::rpcNestedTests()
     QVERIFY_EXCEPTION_THROWN(RPCConsole::RPCExecuteCommandLine(result, "rpcNestedTest(abc,,)"), std::runtime_error); //don't tollerate empty arguments when using ,
 #endif
 
+    UnloadBlockIndex();
     delete pcoinsTip;
+    pcoinsTip = nullptr;
     delete pcoinsdbview;
+    pcoinsdbview = nullptr;
     delete pblocktree;
+    pblocktree = nullptr;
 
     boost::filesystem::remove_all(boost::filesystem::path(path));
 }