[Fix][UT]Fix AbfsFileSystemBehaviorITCase fails with "Bind Address already in use" in CI

[litiliu]

Purpose

Linked issue: close #2629
Fix flaky Azure filesystem ITs caused by the mock auth server binding to a fixed port. Use a random available port and wire it into the test configs to avoid port collisions in CI.

Brief change log

Bind MockAuthServer to an ephemeral port instead of hardcoded 8080
Expose the actual port via getPort()
Update AbfsFileSystemBehaviorITCase and AzureDelegationTokenProviderTest to use the dynamic endpoint

Tests

existing IT

API and Format

Documentation

[litiliu]

@luoyuxia please approve the workflows.

[Copilot]

Pull request overview

Fixes flaky Azure filesystem integration tests in CI by removing a hard-coded mock auth server port and switching to an ephemeral port that is propagated into test configuration (linked to #2629).

Changes:

• Bind MockAuthServer to an ephemeral port (bind(0)) and expose the selected port via getPort().
• Update Azure filesystem IT/UT to build the OAuth endpoint from localhost:<selectedPort>.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
fluss-filesystems/fluss-fs-azure/src/test/java/org/apache/fluss/fs/azure/token/MockAuthServer.java	Bind to port 0, capture the chosen local port, and expose it to callers.
fluss-filesystems/fluss-fs-azure/src/test/java/org/apache/fluss/fs/azure/token/AzureDelegationTokenProviderTest.java	Use the mock server’s dynamically assigned port for the token endpoint.
fluss-filesystems/fluss-fs-azure/src/test/java/org/apache/fluss/fs/azure/AbfsFileSystemBehaviorITCase.java	Configure the ABFS OAuth endpoint using the dynamically assigned port.

Comments suppressed due to low confidence (1)

fluss-filesystems/fluss-fs-azure/src/test/java/org/apache/fluss/fs/azure/token/MockAuthServer.java:76

• run() catches InterruptedException and immediately wraps it in a RuntimeException without restoring the thread interrupt flag. This can cause higher-level test/framework code to miss the interrupt signal. Consider calling Thread.currentThread().interrupt() before rethrowing (or use syncUninterruptibly() if appropriate).

            channelFuture = b.bind(0).sync();
            InetSocketAddress address = (InetSocketAddress) channelFuture.channel().localAddress();
            this.port = address.getPort();
            return channelFuture;
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }

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