* Docs: Fix calls to pagination.Pager.AllPages()

The doc example for `openstack/common/extension` would otherwise fail
compilation with:

    extensions.List(networkClient).Allpages undefined (type pagination.Pager has no field or method Allpages, but does have AllPages)

* Fix formatting issue with doc examples

Some doc examples were wrongly calling `fmt.Println()` with a formatting
specifier instead of `fmt.Printf()`. This caused the examples to print
the literal string `%+v` with a new line before printing the argument
using its default format. This clears the following compilation warning:

    Println call has possible formatting directive %+v

Got all files with `ag "Println.+%"`.