update docstring param description
update docstring param description

Change-Id: I794a42eee5134f925921656e3855d49a895fa35c

mikalstill/nova,klmitch/nova,openstack/nova,mikalstill/nova,gooddata/openstack-nova,klmitch/nova,gooddata/openstack-nova,gooddata/openstack-nova,gooddata/openstack-nova,mikalstill/nova,rahulunair/nova,openstack/nova,rahulunair/nova,phenoxim/nova,phenoxim/nova,mahak/nova,klmitch/nova,klmitch/nova,openstack/nova,mahak/nova,mahak/nova,rahulunair/nova