veyron2/ipc: change Lookup to take second arg that is the method being invoked.

 - update all uses of Lookup
 - rename SoloDispatcher to LeafDispatcher (since that seems like a better
  name) and create a RootDispatcher which doesn't have the test that
  LeafDispatcher does. Update all uses.

Arguably, these should be separate CLs, but since I lumped together
since they touch many of the same files.

Change-Id: I8b7aab4abecbf702f49a3851c50c48e596b6da57
54 files changed
tree: 5550ba8207e07b0a3db2f129029ad4fe575ae7fa
  1. examples/
  2. lib/
  3. products/
  4. runtimes/
  5. security/
  6. services/
  7. tools/