Fix transient fault handling for Pooled connections (#637)

Author: cheenamalhotra

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlInternalConnectionTds.cs

@@ -544,6 +544,8 @@ private bool IsTransientError(SqlException exc)
             {
                 if (s_transientErrors.Contains(error.Number))
                 {
+                    // When server timeouts, connection is doomed. Reset here to allow reconnect.
+                    UnDoomThisConnection();
                     return true;
                 }
             }
@@ -1628,7 +1630,7 @@ private bool AttemptRetryADAuthWithTimeoutError(SqlException sqlex, SqlConnectio
             timeout.Reset();
             // When server timeout, the auth context key was already created. Clean it up here.
             _dbConnectionPoolAuthenticationContextKey = null;
-            // When server timeout, connection is doomed. Reset here to allow reconnect.
+            // When server timeouts, connection is doomed. Reset here to allow reconnect.
             UnDoomThisConnection();
             // Change retry state so it only retries once for timeout error.
             _activeDirectoryAuthTimeoutRetryHelper.State = ActiveDirectoryAuthenticationTimeoutRetryState.Retrying;

src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/SqlInternalConnectionTds.cs

@@ -632,6 +632,8 @@ private bool IsTransientError(SqlException exc)
             {
                 if (transientErrors.Contains(error.Number))
                 {
+                    // When server timeouts, connection is doomed. Reset here to allow reconnect.
+                    UnDoomThisConnection();
                     return true;
                 }
             }
@@ -1976,7 +1978,7 @@ private bool AttemptRetryADAuthWithTimeoutError(SqlException sqlex, SqlConnectio
             timeout.Reset();
             // When server timeout, the auth context key was already created. Clean it up here.
             _dbConnectionPoolAuthenticationContextKey = null;
-            // When server timeout, connection is doomed. Reset here to allow reconnect.
+            // When server timeouts, connection is doomed. Reset here to allow reconnect.
             UnDoomThisConnection();
             // Change retry state so it only retries once for timeout error.
             _activeDirectoryAuthTimeoutRetryHelper.State = ActiveDirectoryAuthenticationTimeoutRetryState.Retrying;