Upon startup peer was scanning all blocks for each
channel's config block. This was extremely
inefficient for large chains.
This change navigates directly to the config block
based on the last block's metadata which has a pointer
to the last config block.

Change-Id: Ia570f4d64df135e99a24a4206006bb969c7e4476
Signed-off-by: David Enyeart <enyeart@us.ibm.com>