Use built-in exception filtering for GreenletExit

Python handles this natively.

Change-Id: I440b87112826f44f4c9c3b4bbdd161d2e202341b
Add a manual page for heat-db-setup

Change-Id: I628d9e1295238b0bc405fc6ccb464889b85090e0
Fixes: Bug #1153691
Merge "Use built-in exception filtering for GreenletExit"
Merge "Add a manual page for heat-db-setup"