[SPARK-29028][DOCS] Add links to IBM Cloud Object Storage connector in cloud-integration.md

### What changes were proposed in this pull request?
Add links to IBM Cloud Storage connector in cloud-integration.md

### Why are the changes needed?
This page mentions the connectors to cloud providers.  Currently connector to
IBM cloud storage is not specified. This PR adds the necessary links for
completeness.

### Does this PR introduce any user-facing change?
Yes.

**Before:**
<img width="1234" alt="Screen Shot 2019-09-09 at 3 52 44 PM" src="https://user-images.githubusercontent.com/14225158/64571863-11a2c080-d31a-11e9-82e3-78c02675adb9.png">

**After.**

<img width="1234" alt="Screen Shot 2019-09-10 at 8 16 49 AM" src="https://user-images.githubusercontent.com/14225158/64626857-663e4e00-d3a3-11e9-8fa3-15ebf52ea832.png">

### How was this patch tested?
Tested using jykyll build --serve

Closes #25737 from dilipbiswal/ibm-cloud-storage.

Authored-by: Dilip Biswal <dbiswal@us.ibm.com>
Signed-off-by: Sean Owen <sean.owen@databricks.com>

Author: dilipbiswal

docs/cloud-integration.md

@@ -257,4 +257,5 @@ Here is the documentation on the standard connectors both from Apache and the cl
 * [Amazon EMR File System (EMRFS)](https://docs.aws.amazon.com/emr/latest/ManagementGuide/emr-fs.html). From Amazon
 * [Google Cloud Storage Connector for Spark and Hadoop](https://cloud.google.com/hadoop/google-cloud-storage-connector). From Google
 * [The Azure Blob Filesystem driver (ABFS)](https://docs.microsoft.com/en-us/azure/storage/blobs/data-lake-storage-abfs-driver)
+* IBM Cloud Object Storage connector for Apache Spark: [Stocator](https://github.com/CODAIT/stocator), [IBM Object Storage](https://www.ibm.com/cloud/object-storage), [how-to-use-connector](https://developer.ibm.com/code/2018/08/16/installing-running-stocator-apache-spark-ibm-cloud-object-storage). From IBM