Credential option should not be 'required' when creating webhook
Credential option should not be 'required' when creating webhook

Change-Id: I4459f410c8bb5c681c66c9dd3f0ba4b3580e57d3

stackforge/python-senlinclient,openstack/python-senlinclient,stackforge/python-senlinclient,openstack/python-senlinclient