[Backport stable/1.3] fix(log/stream): ensure the appender future always gets completed

[romansmirnov]

Description

Related issues

backports #8605
relates #7992

Definition of Done

Not all items need to be done depending on the issue and the pull request.

Code changes:

• The changes are backwards compatibility with previous versions
• If it fixes a bug then PRs are created to backport the fix to the last two minor versions. You can trigger a backport by assigning labels (e.g. backport stable/0.25) to the PR, in case that fails you need to create backports manually.

Testing:

• There are unit/integration tests that verify all acceptance criterias of the issue
• New tests are written to ensure backwards compatibility with further versions
• The behavior is tested manually
• The change has been verified by a QA run
• The impact of the changes is verified by a benchmark

Documentation:

• The documentation is updated (e.g. BPMN reference, configuration, examples, get-started guides, etc.)
• New content is added to the release announcement

[lenaschoenburg]

bors r+

[ghost]

Build failed:

• continuous-integration/jenkins/branch

[lenaschoenburg]

Flaky test.

bors retry

[ghost]

Build succeeded:

• continuous-integration/jenkins/branch