Update the cppsuite logging code to use function calls wrapped in macros.

In order to avoid unnecessary string allocations when we call log_msg() with trace_type greater than _trace_level we should use macros that will check log level before calling the log method. It can look similar to this:  

#define LOG(lvl, msg) \

do { \

    if (_trace_level >= lvl) \

        log_msg(lvl, msg); \

} while (0)