trivial: dump SIGUSR2 stacks to log, not stderr

Change-Id: I036f8a4cb21e03a8c25eb5d761d724682b2f521c
OS-248: no local db calls from cobalt-compute

This patch forbids local db calls from cobalt-compute if conductor is being
used.

Change-Id: I2920e47abe53b1abd07389b76686f45047cadc20
Merge 'trivial: dump SIGUSR2 stacks to log, not stderr' from grizzly/1.5

Change-Id: I0e0c55bf82943cd016fc4445d4f569446f144164
Merge 'OS-248: no local db calls from cobalt-compute' from grizzly/1.5

Added conductor indirection API for nova.objects because nova.objects
was introduced in Havana.

Change-Id: Ibba2101cbb91456297796b4458d6b10e75c1b549