fix: delay call to client in scrollToEnd (#1062)

[web-padawan]

Cherry-pick to 4.2 branch

[vaadin-bot]

SonarQube analysis reported 27 issues

• 2 critical
• 8 major
• 16 minor
• 1 info

Top 10 extra issues

Note: The following issues were found on lines that were not modified in the pull request. Because these issues can't be reported as line comments, they are summarized here:

1. Grid.java#L2327: Remove usage of generic wildcard type.
2. Grid.java#L2971: Define a constant instead of duplicating this literal "direction" 4 times.
3. Grid.java#: This file has 1,694 lines, which is greater than 750 authorized. Split it into smaller files.
4. Grid.java#L1886: Call "Optional#isPresent()" before accessing the value.
5. Grid.java#L1887: Either log or rethrow this exception.
6. Grid.java#L1906: Either log or rethrow this exception.
7. Grid.java#L2784: Call "Optional#isPresent()" before accessing the value.
8. Grid.java#L2794: Call "Optional#isPresent()" before accessing the value.
9. Grid.java#L3485: Rename "editor" which hides the field declared at line 1156.
10. Grid.java#L3895: Remove this unused method parameter "event".