packaging: added numpy as a deps

This patch adds python library numpy as a dependency of
ovirt-websocket-proxy package.

The library is an optional dependency of python-websockify and can lead
to improved performance of console clients using websocket proxy (noVNC,
SPICE-HTML5).

Change-Id: I496416c660bef09f628fe8344774e8b555a06e34
Signed-off-by: Frantisek Kobzik <fkobzik@redhat.com>
Bug-Url: https://bugzilla.redhat.com/1045042