Remove novnc from vncproxy packages list for Ubuntu

Package resources can no longer have array for name since Puppet 3.4.

Since the package nova-novncproxy already requires novnc,
we can safely remove it from the list of packages to install.

Closes-bug: #1263293
Change-Id: Iba7ff0b7aedd750a54d931e0e8cbe37418ed6aed
(cherry picked from commit d4a8c904b775114a10edf5b1a696d6fcbf50e924)