Install and enable apache uwsgi proxy

The uwsgi proxy version that comes with Ubuntu xenial is too old, so
we have to build it from source. This is a temporary solution until
the next LTS.

This lays the ground work for using it in keystone.

Change-Id: I00fb1759e6988c7df0ce0f3df5ff1ce9fd7cd381
diff --git a/stack.sh b/stack.sh
index 635a328..e12b3fe 100755
--- a/stack.sh
+++ b/stack.sh
@@ -780,6 +780,9 @@
 # Install Oslo libraries
 install_oslo
 
+# Install uwsgi
+install_apache_uwsgi
+
 # Install client libraries
 install_keystoneauth
 install_keystoneclient