add numpy to package list, saves lots of time

websockify was added to the pip requires, and it has a dependency
of numpy. Because we didn't specify it in the package list, it was
built from source every time, adding 3 minutes to an average run.

Stop testing whether numpy compiles 100 times a day in CI.

Change-Id: Ic9d9b8135a917deb846911c6b266aec87d05781a
diff --git a/files/apts/nova b/files/apts/nova
index b7d1e92..39b4060 100644
--- a/files/apts/nova
+++ b/files/apts/nova
@@ -31,6 +31,7 @@
 python-libxml2
 python-routes
 python-netaddr
+python-numpy # used by websockify for spice console
 python-pastedeploy
 python-eventlet
 python-cheetah