Move sync_with_stdio into TestConnections constructor

This way all tests run with the same configuration.

maxscale-system-test/mysqlmon_switchover.cpp

@@ -172,8 +172,6 @@ void run(TestConnections& test)
 
 int main(int argc, char* argv[])
 {
-    std::ios::sync_with_stdio(true);
-
     Mariadb_nodes::require_gtid(true);
     TestConnections test(argc, argv);