Enhance checks on LCM in SystemValidator

[phfriedrich]

As discussed with @TuemmlerKelch, we should improve checks on the LCM state.
Currently we check for LCMStateDetail -ne "" , when trying to figure out, if the LCM is busy.

However, there is also LCMState, that we could use. It informs us about the current state of the LCM immediately.
We should then wait until the state is Idle. The following states are possible:

• Idle (as soon as configuration, reboot, checks, etc. have been finished)
• Busy (Checks currently running, configurations are being applied)
• PendingReboot (configurations have been applied, but reboot is required)
• PendingConfiguration (configuration has been rolled out, but must still be applied)

Also, we can reduce the timeout after checking for the state of LCM to five seconds (currently 20 seconds).