Utilize pypi-mirror from tripleo-cd

We want to use the local mirror if we can.

Requires I208ac2c316cf76fe928062d8a1c98a02aa1dff1c to be effective but
can be merged before it lands.

Change-Id: I61e432ad46abd29e332417b19b61d7835d0de772

elements/tripleo-cd/element-deps

@@ -1 +1,2 @@
 source-repositories
+pypi-mirror

elements/tripleo-cd/install.d/10-tripleo-cd

@@ -37,4 +37,7 @@ else
     exit 1
 fi
 
+mkdir -p ~root/.cache/image-create
+ln -s /var/cache/pypi-mirror/pypi ~root/.cache/image-create
+
 install -m 0755 -o root -g root $(dirname $0)/../tripleo-cd.sh /usr/local/bin

elements/tripleo-cd/tripleo-cd.sh

@@ -17,6 +17,7 @@
 
 set -eux
 
+export OVERCLOUD_DIB_EXTRA_ARGS=pypi
 while true; do
     source /opt/stack/tripleo-incubator/scripts/refresh-env /opt/stack
     source /root/stackrc