upload-health: Removing pxemgnr support

The automatic health check doesn't use the pxemgnr, so let's remove all
this dead code.
upload-health: Insure proper reading of config file

Prior this commit the configuration file wasn't parsed properly and lead
to an upload in /etc which is forbiden.
upload-health: Allow multiple upload on same dir

When benchmarking several hosts at the same time they do try uploading
theirs resultst on the same time. As the directory was already existing,
only the first system that uploaded its result got saved.

This patch insure that if the directory already exists, meaning another
host already uploaded some result in the same minute, the uploading
doesn't fail.