Resolve "Error reading commit status in JenkinsDeprecatedService"

What does this MR do?

• Properly generates the build hook URL in compose_service_hook
• Handles non-matching responses

Are there points in the code the reviewer needs to double check?

N/A

Why was this MR needed?

JenkinsDeprecatedService is very fragile and doesn't handle responses from the Jenkins instance that don't match the expected format.

Screenshots (if relevant)

N/A

Does this MR meet the acceptance criteria?

• N/A Changelog entry added, if necessary
• N/A Documentation created/updated
• N/A API support added
• N/A Tests added for this feature/bug
• Review
  • N/A Has been reviewed by UX
  • N/A Has been reviewed by Frontend
  • Has been reviewed by Backend
  • N/A Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• N/A Internationalization required/considered
• N/A If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan

What are the relevant issue numbers?

Closes #3335 (closed)