[repack] Corrected the problem of Agent ownership removal for repack request and repack sub-requests

Adding some checks on available rpms to fail Docker build phase if there is no point going further (with some diagnostics)

Updated cta-taped.conf.example to show how to disable the Repack Request Management on the tapeserver

[cta-taped] The repack management can be enabled or disabled via the DisableRepackManagement parameter in the configuration file

[RAO] If the drive limits UDS could not be queried, the RAO is not disabled anymore. A CTA RAO is triggered.

This reverts commit b17463e8.

And improve starting of old and new versions of mhvlt when creating buildtree environment

By default all packages will be taken from public repositories. Run `./bootstrapCTA.sh cern` and `./bootstrapMHVTL.sh cern` to get packages from cern-only repos.

This reverts commit db9085e6.

utils::trimString() now returns an empty string if the string passed in parameter contains only white-space characters

Fixed

[lto_rao] Added a timer to measure the execution time of the RAO algorithm (instanciation + execution)