gridevents: immediatly fix cluster blacklists when a user uses "gridevents -f"

[jgaida]

Child events like cluster blacklists should be fixed immediately. It is very confusing that cluster blacklists stay for a while (when parent events are fixed and not displayed anymore).

[jgaida]

We can also list events that have been fixed in stdout to give a feedback to users.

[bzizou]

I have to check if it is possible and if it does not lead to coherency problems. In the worst case, we could simply hide blacklists events attached to fixed events.