changed time query function: FDateTime::Now() to FDateTime::UtcNow()

[stereoboy]

I thought that FDateTime::UtcNow() is better than FDateTime::Now(). FDateTime::Now() returns local time. But ROS's Time::Now() implementation uses gettimeofday() or clock_gettime() and all the functions return UTC. (https://docs.ros.org/api/rostime/html/src_2time_8cpp_source.html. )

Please review it.

[andreihaidu]

Thanks for noticing this!