Performs hard reboot if libvirt soft reboot raises libvirtError

Currently the libvirt driver will only attempt a hard reboot if a soft
reboot fails and returns False. If a libvirt exception is raised,
however, the hard reboot is not attempted. This patch wraps the soft
reboot in a try block to continue with the hard reboot attempt if a
libvirtError is raised.

Fixes bug 1202974

(cherry picked from commit 9925c9f1b353240ebb1eccde50574055ce271313)

Conflicts:
	nova/tests/test_libvirt.py

Change-Id: Ifaff75b33b5123cdd3293e8f263ccb4f72ae726a
Fixes host stats for VMWareVCDriver

Host stats for VCDriver should collect aggregate cluster stats
rather than that of a single host in the cluster.

Fixes: bug #1190515
Change-Id: I37e46995c5da2e3052e8178098afee7c8061bb3c
(cherry picked from commit 92983257bb8e19dff54cc8a2188cc692dcafe5b8)
Merge "Fixes host stats for VMWareVCDriver" into stable/grizzly
Merge "Performs hard reboot if libvirt soft reboot raises libvirtError" into stable/grizzly
Merge branch 'stable/grizzly' of https://github.com/openstack/nova into kbenton/ivssupport_grizzly