etcd.sh should check etcd_info folder of must-gather

[palonsoro]

Recent versions of must-gather include some interesting etcd information populated in etcd_info by gather_etcd script. Some of that info can be interesting to be checked.

Examples that could be checked:

• alarm_list.json: No alarm should be listed here
• There should be 1 or 3 members as per member list
• There should be one leader only, neither more than one nor zero
• Getting endpoint health should not return a took higher than some threshold (not sure if 50ms would be a good threshold here)
• DB sizes and quotas can be checked from here
• Differences of applied indexes should not be higher than a threshold (here I am not also fully sure on which could be a good threshold, maybe some value between 10 and 50, but I'd prefer a second opinion on this)
• Differences in the raft terms of more than 1 or 2 would be worrying: It would mean that some members are not aware of a new leader being elected, which has high chances of meaning a partition.
• ...