Install requirements.txt for generating cookied models

After introducing gpg keys for secrets.yml, it is required
for model generation

Change-Id: I97c56bd0686f378151a08e5f9c280871e3af3dbe
diff --git a/tcp_tests/templates/shared-salt.yaml b/tcp_tests/templates/shared-salt.yaml
index d48fb6a..bc30a10 100644
--- a/tcp_tests/templates/shared-salt.yaml
+++ b/tcp_tests/templates/shared-salt.yaml
@@ -402,6 +402,10 @@
     popd
     {%- endif %}
 
+    if [ -f /root/cookiecutter-templates/requirements.txt ]; then
+        pip install -r /root/cookiecutter-templates/requirements.txt
+    fi
+
     mkdir -p /srv/salt/reclass/classes/cluster/
     mkdir -p /srv/salt/reclass/classes/system/
     mkdir -p /srv/salt/reclass/classes/service/