Adapt DirectArtifactManagerFactory to run test on IPv6

[imonteroperez]

Highlights

• Current use of URL builder does not cover IPv6
• If we run a test using this code on an IPv6 environment we will get the following exception

java.net.MalformedURLException: Error at index 0 in: "::45033"
	at java.base/java.net.URL.<init>(URL.java:679)
	at java.base/java.net.URL.<init>(URL.java:541)
	at java.base/java.net.URL.<init>(URL.java:488)
	at org.jenkinsci.plugins.workflow.DirectArtifactManagerFactory.<init>(DirectArtifactManagerFactory.java:105)

• This PR changes the URL builder invocation to a compliant one with both IPv4 and IPv6 addresses format

Testing done

• Tested via PCT on an IPv6 environment and working as expected

Submitter checklist

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2. Ensure that the pull request title represents the desired changelog entry
3. Please describe what you did
4. Link to relevant issues in GitHub or Jira
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6. Ensure you have provided tests - that demonstrates feature works or fixes the issue