Improve token credential object caching logic for identity extension (Azure#43936)

Author: moarychan

sdk/identity/azure-identity-extensions/src/main/java/com/azure/identity/extensions/implementation/credential/provider/CachingTokenCredentialProvider.java

@@ -58,7 +58,7 @@ private static TokenCredential getOrCreate(Map<String, TokenCredential> cache,
             LOGGER.verbose("Retrieving token credential from cache.");
         } else {
             LOGGER.verbose("Caching token credential.");
-            cache.put(tokenCredentialCacheKey, fn.apply(delegate));
+            cache.putIfAbsent(tokenCredentialCacheKey, fn.apply(delegate));
         }
 
         return cache.get(tokenCredentialCacheKey);

sdk/identity/azure-identity-extensions/src/test/java/com/azure/identity/extensions/implementation/template/AzureAuthenticationTemplateTest.java

@@ -117,7 +117,7 @@ void nonCacheTokenCredential() {
     }
 
     @Test
-    void getTokenAsPasswordWithDefaultCredentialProvider() throws InterruptedException {
+    void verityTokeWithDefaultCredentialProvider() throws InterruptedException {
         // setup
         String token1 = "token1";
         String token2 = "token2";
@@ -152,7 +152,7 @@ void getTokenAsPasswordWithDefaultCredentialProvider() throws InterruptedExcepti
     }
 
     @Test
-    void getTokenAsPasswordWithCachingCredentialProvider() throws InterruptedException {
+    void verityTokenWithCachingCredentialProvider() throws InterruptedException {
         int tokenExpireSeconds = 2;
         AtomicInteger tokenIndex1 = new AtomicInteger();
         AtomicInteger tokenIndex2 = new AtomicInteger(1);
@@ -180,7 +180,7 @@ void getTokenAsPasswordWithCachingCredentialProvider() throws InterruptedExcepti
 
             verifyToken("token1-", 0, template);
             TimeUnit.SECONDS.sleep(tokenExpireSeconds + 1);
-            verifyToken("token2-", 1, template);
+            verifyToken("token2-", 1, template2);
             assertNotNull(credentialProviderMock);
         }
     }