PCT-565 Protection from invalid caputure

Added a control of time took to collect the metrics.
If it is > 10% of ticker interval, metrics are discarded.
The calculated time include all metrics collected in the run function
because ie if SHOW STATUS takes 3 seconds, all following metrics like
SELECT NAME, ... FROM INFORMATION_SCHEMA.INNODB_METRICS will be
timeshifted, so I think we need to ignore them to keep them synchronized.
To make test more resilient and clear about what we're doing, instead of hard-coded 4, `config.Collect + 1` is better because it shows we only need to delay 1s more than the collect time.  If Collect was float we could just + 0.5 but 1s is ok for now.