monitoring: restore ready_for_holdover status

[vvfedorenko]

Change the sequence of initialisation to provide proper information about SA53 MAC.

[leoleovich]

This is a fix for https://github.com/Orolia2s/oscillatord/issues/111

[agagniere]

However this will revert #90

[leoleovich]

@agagniere is there a way to update "ready for holdover" without blocking a start?

[agagniere]

Yes I will add a commit