doc: Add kubernetes example in Launch an instance
doc: Add kubernetes example in Launch an instance

* Move keypair and image upload up
* Add a kubernetes cluster creation/deletion and deployement
  creation example

Change-Id: I57c99b61acfde872e4be81cb9e0f885a6188d2f6

ArchiFleKs/magnum,openstack/magnum,openstack/magnum,ArchiFleKs/magnum