Improve help text for XenServer Options
Improve help text for XenServer Options

This commit adds additional help text for xenapi_volume_utils_opts
and xenapi_ovs_integration_bridge_opts.

Blueprint centralize-config-options-newton

Change-Id: I0cf1481fd556caf99f74166dfb4bda9992324d28

cloudbase/nova,rajalokan/nova,Juniper/nova,vmturbo/nova,sebrandon1/nova,mikalstill/nova,Juniper/nova,sebrandon1/nova,openstack/nova,klmitch/nova,mikalstill/nova,gooddata/openstack-nova,rahulunair/nova,rajalokan/nova,rahulunair/nova,cloudbase/nova,hanlind/nova,cloudbase/nova,gooddata/openstack-nova,alaski/nova,mahak/nova,hanlind/nova,vmturbo/nova,gooddata/openstack-nova,rahulunair/nova,alaski/nova,jianghuaw/nova,phenoxim/nova,sebrandon1/nova,klmitch/nova,klmitch/nova,mahak/nova,vmturbo/nova,jianghuaw/nova,mikalstill/nova,jianghuaw/nova,vmturbo/nova,openstack/nova,rajalokan/nova,openstack/nova,Juniper/nova,Juniper/nova,jianghuaw/nova,phenoxim/nova,rajalokan/nova,mahak/nova,hanlind/nova,gooddata/openstack-nova,klmitch/nova