Rename download config to config download

This aligns better with other interfaces which are all
openstack overcloud <noun> <verb>

E.g "image upload", "plan export" etc - so "config download" fits better?

Change-Id: Ic46ed75397714e46895bdb44a408f6a10d7b40cf

releasenotes/notes/config_download-5ba7f496b2186b68.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - |
+    A new command "openstack overcloud config download" has been added which
+    enables download of the configuration data used by TripleO for debugging
+    or running outside the control of the overcloud heat stack.  Note that
+    running configuration tools outside of the heat stack experimental at this
+    stage and should be used with caution.

setup.cfg

@@ -64,7 +64,7 @@ openstack.tripleoclient.v1 =
     baremetal_configure_ready_state = tripleoclient.v1.baremetal:ConfigureReadyState
     baremetal_configure_boot = tripleoclient.v1.baremetal:ConfigureBaremetalBoot
     overcloud_netenv_validate = tripleoclient.v1.overcloud_netenv_validate:ValidateOvercloudNetenv
-    overcloud_download_config = tripleoclient.v1.overcloud_config:DownloadConfig
+    overcloud_config_download = tripleoclient.v1.overcloud_config:DownloadConfig
     overcloud_container_image_upload = tripleoclient.v1.container_image:UploadImage
     overcloud_container_image_build = tripleoclient.v1.container_image:BuildImage
     overcloud_container_image_prepare = tripleoclient.v1.container_image:PrepareImageFiles