Limit inspector jobs to 1 testing VM
Limit inspector jobs to 1 testing VM

Currently ironic-base defaults to 2 and our tests try to introspect
all of them. This puts unnecessary strain on the CI systems, return
the number back to 1.

Change-Id: I820bba1347954b659fd7469ed542f98ef0a6eaf0

openstack/ironic,openstack/ironic