Dashboards: PT Summary does not refresh correctly

User impact:

Wrong System/Service summary can be displayed

Steps to reproduce:
Go to Node Summary dashboard
Wait for System Summary of pmm-server to load
Select another node in Node Name filter

Actual result:

All graphs refresh to show values of another node but System Summary of pmm-server is still displayed

Expected result:

System Summary of another node should be displayed

Workaround:

Refresh manually

Details:

• In PMM 2.26.0 StartPTSummary request was sent on every filter change, in 2.28.0 it's based on refresh dashboard settings (1m by default)
• All PT Summary panels affected