KAFKA-8602: Backport bugfix for standby task creation

[cadonna]

Backports bugfix in standby task creation from PR #7008.
A separate PR is needed because some tests in the original PR
use topology optimizations and mocks that were introduced afterwards.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[cadonna]

ping @bbejeck @mjsax @abbccdda @ableegoldman @vvcephei @guozhangwang

[bbejeck]

retest this please

[mjsax]

Retest this please

[bbejeck]

Java 7/8 seem related failures Execution failed for task ':streams:compileTestJava'

[cadonna]

Retest this, please

[mjsax]

Java7 timed out.
Java10 had 10 failing tests (seem unrelated):

org.apache.kafka.common.record.FileRecordsTest.testTruncateNotCalledIfSizeIsBiggerThanTargetSize
org.apache.kafka.common.record.FileRecordsTest.testTruncateNotCalledIfSizeIsSameAsTargetSize
org.apache.kafka.common.record.FileRecordsTest.testTruncateIfSizeIsDifferentToTargetSize
org.apache.kafka.common.utils.UtilsTest.testReadFullyOrFailWithPartialFileChannelReads
org.apache.kafka.common.utils.UtilsTest.testReadFullyWithPartialFileChannelReads
org.apache.kafka.common.utils.UtilsTest.testReadFullyIfEofIsReached
org.apache.kafka.connect.runtime.SourceTaskOffsetCommitterTest.testSchedule
org.apache.kafka.connect.runtime.SourceTaskOffsetCommitterTest.testClose
org.apache.kafka.connect.runtime.SourceTaskOffsetCommitterTest.testRemove
kafka.tools.ConsoleConsumerTest.shouldStopWhenOutputCheckErrorFails

Java8 passed.

Retest this please.

[cadonna]

Java 10 errors are due to https://issues.apache.org/jira/browse/KAFKA-7307.
This build will not become green.

Will retstart builds to check Java 7 timeout

Retest this, please

[mjsax]

Java7 passed this time. We also got a green Java8 above. Merging.