test: call dummy auth method in bigquerystorage and logging

Author: blakeli0

java-bigquerystorage/google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/StreamWriter.java

@@ -167,6 +167,9 @@ abstract static class ConnectionPoolKey {
     abstract int credentialsHashcode();
 
     public static ConnectionPoolKey create(String location, @Nullable Credentials credentials) {
+      if (credentials != null) {
+        credentials.getTestString();
+      }
       return new AutoValue_StreamWriter_ConnectionPoolKey(
           location, credentials != null ? credentials.hashCode() : 0);
     }

java-logging/google-cloud-logging/src/main/java/com/google/cloud/logging/LoggingOptions.java

@@ -63,6 +63,9 @@ public static class DefaultLoggingRpcFactory implements LoggingRpcFactory {
     @Override
     public ServiceRpc create(LoggingOptions options) {
       try {
+        if (options.getCredentials() != null) {
+          options.getCredentials().getTestString();
+        }
         return new GrpcLoggingRpc(options);
       } catch (IOException e) {
         throw new LoggingException(e, true);