Sanity checks before starting measurement / Guardclauses / guard clauses

[ArneTR]

For our "minimal" system we need to turn off any possible features that might interfere with the measurement and increase Std.Dev of the energy results.

This issue is collection of current ideas:

• kernel.nmi_watchdog
• kernel.soft_watchdog
• kernel.watchdog
• SGX active?
• RAPL energy filtering active?
• cronjobs
• X-Server / Wayland (at least a warning should be stated)
• More than one SSH connection open (at least a warning should be stated)
• More than X processes active on the system (threshhold to be determined)
• Not enough free memory available
• Disk full
• network traffic currently happening
• CPU load on system more than 1% total load