Created attachment 837123 [details]
screenshot

Description of problem:
There is a possibility to configure a custom interval in Metrics tab.
It is applied to metrics sharts, but not completely applied to availability line. Availability chart interval has the same lenght as expected, but its end is always a current moment - as fact, it is "Last <custom interval length>".

How reproducible:
Always for me

Steps to Reproduce:
1. Open Monitoring-Metrics tab for any resource.
2. Click Custom button in the interval selection band and configure some interval in the past - its start and end should be before the current moment. Apply.

Expected results:
2. Selected interval has been applied to availability line and all available metrics charts.

Actual results:
2. Metrics charts are OK, but Availability is NOK.

See screenshot.
1 - selected interval is 7:09 - 7:12 (3 minutes length).
2 - metric shart is shown for expected interval
3 - availability line is shown for the last 3 minutes - the used interval has the same length as a configured one, but its end is a current moment.