release: Don't publish CW if !WITH_CLOUDWARE

If WITH_CLOUDWARE is not set, we didn't build BASIC-CLOUDWARE; don't try
to install it into the /VM-IMAGES/ directory as part of ftp-stage.

Fixes: 4771c2e9d1c7 "release: Publish non-uploaded cloudware bits"
MFC after: 6 days

(cherry picked from commit 836f00ebb96ac343e0f8a68ea264d2d330198488)