Standardize usage of client arguments (config-reference)

Like documented at https://wiki.openstack.org/wiki/Documentation/Conventions#Client_arguments:_.22--option_ARGUMENT.22
we prefer to use '--option ARGUMENT'.

Change-Id: Iea99bbd253ee4ced00ab9983c00ebc805e6e7568
Merge "Standardize usage of client arguments (config-reference)"