Fixed name of ibm-api-key in cli

Author: mikewurtz

SoftLayer/CLI/image/export.py

@@ -12,7 +12,7 @@
 @click.command()
 @click.argument('identifier')
 @click.argument('uri')
-@click.option('--ibm_api_key',
+@click.option('--ibm-api-key',
               default="",
               help="The IBM Cloud API Key with access to IBM Cloud Object "
                    "Storage instance.")