Make readOnlyBearerAuth volatile to prevent data races when executing concurrently doPullBearerAuth() and/or doPushBearerAuth()

Author: raulpardo

jib-core/src/main/java/com/google/cloud/tools/jib/registry/RegistryClient.java

@@ -237,7 +237,7 @@ static Multimap<String, String> decodeTokenRepositoryGrants(String token) {
 
   // mutable
   private final AtomicReference<Authorization> authorization = new AtomicReference<>();
-  private boolean readOnlyBearerAuth;
+  private volatile boolean readOnlyBearerAuth;
   private final AtomicReference<RegistryAuthenticator> initialBearerAuthenticator =
       new AtomicReference<>();