ticket-777: Fix the bug when IMDS fails during auth token refresh whi…

[k2chogori]

Summary

Fixes #777.

When a token refresh fails before the federation request is made, concurrent callers can remain blocked waiting for the shared in-flight refresh result until the timeout expires.

This change ensures that every leader-side refresh failure:

• completes the shared refresh future exceptionally, releasing current waiting callers immediately;
• clears the in-flight state so a subsequent caller can begin a new refresh.

The refresh logic is extracted into a focused helper while preserving the existing public API and error behavior.

Testing

• Added a regression test that simulates a failed refresh of the client certificate before the token request.

• Verified that a concurrent caller receives the leader’s failure promptly rather than waiting for the single-flight timeout.

• Ran:

  mvn -pl bmc-common -Dtest=X509FederationClientTest test
  

  Result: 7 tests passed.

[2026/07/29 14:47:02] vianovak ~/workspace/oci-java-sdk [github-777] $ export JAVA_HOME=/Users/vianovak/Library/Java/JavaVirtualMachines/corretto-1.8.0_422/Contents/Home                             
export PATH="$JAVA_HOME/bin:$PATH"
mvn -pl bmc-common -Dtest=X509FederationClientTest test
...
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running com.oracle.bmc.auth.internal.X509FederationClientTest
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
[INFO] Tests run: 7, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 3.894 s -- in com.oracle.bmc.auth.internal.X509FederationClientTest
[INFO] 
[INFO] Results:
[INFO] 
[INFO] Tests run: 7, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] 
[INFO] --- animal-sniffer:1.16:check (animal-sniffer-check) @ oci-java-sdk-common ---
[INFO] Checking unresolved references to org.codehaus.mojo.signature:java18:1.0
[INFO] /Users/vianovak/workspace/oci-java-sdk/bmc-common/src/main/java/com/oracle/bmc/http/signing/pki/Eraser.java:23: Covariant return type change detected: java.nio.Buffer java.nio.ByteBuffer.clear() has been changed to java.nio.ByteBuffer java.nio.ByteBuffer.clear()
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  6.576 s
[INFO] Finished at: 2026-07-29T14:49:19Z
[INFO] ------------------------------------------------------------------------

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