Add requirements jobs for rally

Change-Id: I4ef9be4bbb2b7e6fd339894d50c92db69b9f9ee7
Give Zuul file descriptor breathing room.

The Zuul service opens a lot of TCP connections and files resulting in
many open file descriptors. The default limit of 2048 is bumped into
regularly. Bump the limit to 8192 when starting the Zuul service to give
it breathing room to grow into.

Change-Id: I9a3aee664c1c6c6139b012fc3dc0631725f59741
Merge "Give Zuul file descriptor breathing room."
Merge "Add requirements jobs for rally"