rstrnt-report-log prints stuff to stdout

[AloisMahdal]

rstrnt-report-log will print things like "Uploading ... .done" to stdout, which breaks use cases where stdout is being generated and needs to have proper format. (E.g. meta-programming.)

I didn't keep restraint version number as I reproduced it (I blamed beakerlib which turned innocent), but:

https://github.com/p3ck/restraint/blob/c62e8c86e9af36e370f8eaaefbbc4ba8694154b5/src/cmd_log.c#L111

Thanks @hegerj for finding the line for me.

[AloisMahdal]

If someone tells me what should be the function I can make PR (and pretend I know C).