Only load the container on flow pages

Profiling was showing flow code taking longer than other extensions
to initialize.  To reduce the amount of code run on non-flow pages
I have pulled two variables out of the container and initialized
them in FlowHooks from the extension initialization.  This brings
flow in-line with other extensions in the time it takes to initialize.

Change-Id: Ief1490edd04c82ebe1eab7b13aaa2ba6da78b73f
Merge "Only load the container on flow pages"