Robustify shocco install and config

* shocco has some non-optional prereqs, make sure they are present if
shocco is being installed
* set the path to installed shocco correctly
* add the working dir to .gitignore

Change-Id: If786ea9e28d3595775f7b86d2fe760dff8047f49
diff --git a/.gitignore b/.gitignore
index 0c22c6b..a3d5b0d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,5 +13,6 @@
 accrc
 .stackenv
 .prereqs
+devstack-docs-*
 docs/
 docs-files