8274793: Suppress warnings on non-serializable non-transient instance fields in sun.net

Reviewed-by: alanb

src/java.base/share/classes/sun/net/www/http/KeepAliveCache.java

@@ -79,6 +79,7 @@ public class KeepAliveCache
 
     // This class is never serialized (see writeObject/readObject).
     private final ReentrantLock cacheLock = new ReentrantLock();
+    @SuppressWarnings("serial") // Type of field is not Serializable
     private Thread keepAliveTimer = null;
 
     /**

src/java.base/unix/classes/sun/net/www/protocol/http/ntlm/NTLMAuthentication.java

@@ -119,8 +119,10 @@ public class NTLMAuthentication extends AuthenticationInfo {
         });
     };
 
+    @SuppressWarnings("serial") // Type of field is not Serializable
     PasswordAuthentication pw;
 
+    @SuppressWarnings("serial") // Type of field is not Serializable
     Client client;
     /**
      * Create a NTLMAuthentication: