Clean some parts in bash script control_rancid

[earendilfr]

• allow the possibility to send the output of the rancid_run to stderr (-d)
• allow the possibility to send the log to only one file
• change some lines for in control_rancid to be more "readable"

Part of these changes would be usefull for another pull request I will provide after

[earendilfr]

Erratum in "control_rancid" file... Correction done in other pull request provided