[FAB-5855] CouchDB bulk update serviceability

CouchDB bulk retrieve and bulk update functions have recently
been added. This change improves readability, maintainability,
serviceability by clarifying code, adding comments, adding
debug.

Change-Id: I552455003ce582288b059f6b434c3d6b93a0688d
Signed-off-by: David Enyeart <enyeart@us.ibm.com>

Author: denyeart