fix: Use distributor 0.18.0 for Keptn 0.18.0 compatibility

[christian-kreuzberger-dtx]

During testing I noticed that jmeter-service does not work with Keptn 0.18, and I got the following error message:

time="2022-08-29T09:54:22Z" level=info msg="Loading jmeter/jmeter.conf.yaml for sockshop.dev.carts"
time="2022-08-29T09:54:22Z" level=info msg="error when trying to load jmeter/jmeter.conf.yaml file for service carts on stage dev or project-level sockshop"
time="2022-08-29T09:54:22Z" level=error msg="Unable to run JMeter tests: error when trying to load jmeter/jmeter.conf.yaml file for service carts on stage dev or project-level sockshop"

This was most likely caused by using an old version of keptn/distributor. Updating fixes it:

[github-actions]

Unit Test Results

20 tests   20 ✔️  1m 0s ⏱️
  1 suites    0 💤
  1 files      0 ❌

Results for commit 0b5580b.

[github-actions]

The following Docker Images have been built:
ghcr.io/keptn-contrib/jmeter-service:0.18.1-dev-PR-5,ghcr.io/keptn-contrib/jmeter-service:0.18.1-dev-PR-5.202208291055

[Raffy23]

LGTM