JCLOUDS-1646: Use boxed Long in GCS

Previously some objects lacked a content-length so this threw a
NullPointerException when unboxing.

Author: gaul

providers/google-cloud-storage/src/main/java/org/jclouds/googlecloudstorage/blobstore/GoogleCloudStorageBlobStore.java

@@ -251,7 +251,7 @@ public Blob getBlob(String container, String name, GetOptions options) {
       MutableBlobMetadata metadata = objectToBlobMetadata.apply(gcsObject);
       Blob blob = new BlobImpl(metadata);
       Payload payload = api.getObjectApi().download(container, Strings2.urlEncode(name), httpOptions).getPayload();
-      long contentLength = payload.getContentMetadata().getContentLength();
+      Long contentLength = payload.getContentMetadata().getContentLength();
       payload.setContentMetadata(metadata.getContentMetadata()); // Doing this first retains it on setPayload.
       blob.setPayload(payload);
       // getObject() returns the full object length but download() could be smaller due to range requests.