Fix docstring of parsing order

There is wrong explaination of option parsing order in config files
and on command line. That is only the later one takes action.
The sample code shows only the later one takes action.
See http://paste.openstack.org/show/64229/

Change-Id: I4d48df1b551bb130dc25fe32303fa2d0b1fecffd
Merge "Fix docstring of parsing order"