fix issues when transaction is unsampled in Kafka instrumentation

[beniwohli]

closes #1578

[ghost]

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• Start Time: 2022-06-30T06:47:16.815+0000

• Duration: 36 min 45 sec

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Test	Results
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Passed	4915
Skipped	3455
Total	8370

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Name	Metrics % (covered/total)	Diff
Packages	100.0% (68/68)	💚
Files	100.0% (227/227)	💚
Classes	100.0% (227/227)	💚
Lines	89.614% (17239/19237)	❕
Conditionals	76.771% (3143/4094)	❕

[basepi]

This needs a CHANGELOG entry as well