[test] Avoid network retries in AzureFileSystemPluginTest

[dstolis]

Purpose

Linked issue: close #4637

AzureFileSystemPluginTest#testCreateWithoutAccountKey took ~637 s on a non-resolvable host because
ABFS retried with exponential backoff. Timings before and after are in the issue.

Brief change log

• Set fs.azure.account.hns.enabled=false, as AbfsFileSystemBehaviorITCase and
  AbfsFileSystemDelegationTokenITCase already do, and fs.azure.io.retry.max.retries=0 as a
  fail-fast safety net.
• Use account.dfs.core.windows.invalid (reserved TLD, RFC 2606) so the host can never resolve or be
  registered.
• testCreateWithAccountKey now uses a base64-encoded dummy key, so initialization completes.
• Both create() tests now assert that create() returns an AzureFileSystem instead of swallowing
  exceptions.

Tests

• AzureFileSystemPluginTest#testCreateWithAccountKey
• AzureFileSystemPluginTest#testCreateWithoutAccountKey

API and Format

No.

Documentation

No.

---

Generated-by: Claude Code (Claude Opus 5.5)

[dstolis]

	main (#4259)	main (#4624)	PR #4640
AzureFileSystemPluginTest	638.6 s	639.6 s	0.643 s
Azure FS module, test phase	10:57 min	10:58 min	23.8 s
Java 11 / core job total	50:22 min	50:19 min	39:44 min