libvirt: Fix infinite loop waiting for block job

Libvirt may return an empty dict when a block job has completed.
In this case, _wait_for_block_job will return True, causing
its callers to loop.

Affects volume_snapshot_delete, swap_volume, and live_snapshot.

(See http://libvirt.org/git/?p=libvirt.git;a=commit;h=0f9e67bf )

Closes-Bug: #1260123
Change-Id: Iab81299f0ce32a14e46aee0fd389ed29f7e503b8
Update nova.conf.sample

Recent version of python-keystoneclient introduces new option,
include_service_catalog, so nova.conf.sample should be updated.

Closes-bug: #1268614
Change-Id: I8f5f76770b8af8002f6a296594303224ec37846c
Merge "libvirt: Fix infinite loop waiting for block job"
libvirt, fix test tpool_execute_calls_libvirt

An exception raised by mock for expected method is obscured
by the "catch Exception" on libvirt/driver.py#643.

This patch updates the test to be more coherent with the code.

Change-Id: I629634395d11432f9d7e4fbe330b864490fa1801