Fix some typos in nova api ref doc
Fix some typos in nova api ref doc

* returnd
* specifiled
* obejct

Change-Id: I57af28fd3934b036c65e284d40ff27d043cd2431

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