Fix race condition in JWT realm test (#138448)

Fix race condition in JwtRealmAuthenticateTests
testJwkUpdatesByReloadWithFile.

The foreground test thread checks the JWT cache without proper locking
or synchronization. The can result in concurrent modification to the
JWT cache and NPE.

This change simply disables the JWT cache for this test.
It isn't relevant to the test.

Author: ebarlas

muted-tests.yml

@@ -408,9 +408,6 @@ tests:
 - class: org.elasticsearch.xpack.ml.integration.RevertModelSnapshotIT
   method: testRevertModelSnapshot_DeleteInterveningResults
   issue: https://github.com/elastic/elasticsearch/issues/132349
-- class: org.elasticsearch.xpack.security.authc.jwt.JwtRealmAuthenticateTests
-  method: testJwkUpdatesByReloadWithFile
-  issue: https://github.com/elastic/elasticsearch/issues/138397
 - class: org.elasticsearch.smoketest.MlWithSecurityIT
   method: test {yaml=ml/start_data_frame_analytics/Test start classification analysis when the dependent variable cardinality is too low}
   issue: https://github.com/elastic/elasticsearch/issues/138409

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/authc/jwt/JwtRealmAuthenticateTests.java

@@ -286,7 +286,7 @@ private void doTestJwkUpdatesByReload(boolean httpsServer) throws Exception {
             1, // audiencesRange
             1, // usersRange
             1, // rolesRange
-            1, // jwtCacheSizeRange
+            0, // jwtCacheSizeRange (disabled cache)
             httpsServer, // createHttpsServer,
             true
         );