Fixed doc example
Fixed doc example

Image.data is a method, not an attribute.

DocImpact

Change-Id: I16555e456dcb2c9719de6c44c01ab68e82ad0590

varunarya10/python-glanceclient,openstack/python-glanceclient,JioCloud/python-glanceclient,JioCloud/python-glanceclient,openstack/python-glanceclient,klmitch/python-glanceclient,varunarya10/python-glanceclient,mmasaki/python-glanceclient,mmasaki/python-glanceclient,klmitch/python-glanceclient