Standardize usage of client arguments (networking-guide)

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

Change-Id: I0481252ff433a7edb52a8670a07a524cc7bd0b8e
Merge "Standardize usage of client arguments (networking-guide)"