Change config option to 'ironic_inspector' and False by default

Change the config option which enables the ironic inspector tests to
'ironic_inspector'. When trying to use 'ironic-inspector = False' it
did not work. Using 'ironic_inspector = False' did work. So to remove
future confusion change the option name to 'ironic_inspector'

Also change the default to False, otherwise the tests are running on
non-inspector test runs and failing. Working around it is difficult
because of the ironic grenade jobs. So change it to default to False.

Change-Id: Ic1d9fbdb1505662ef499229f700dffb719993a90
diff --git a/ironic_tempest_plugin/config.py b/ironic_tempest_plugin/config.py
index aa416b8..96a7f74 100644
--- a/ironic_tempest_plugin/config.py
+++ b/ironic_tempest_plugin/config.py
@@ -23,8 +23,8 @@
                                     help='Whether or not ironic is expected '
                                     'to be available')
 
-inspector_service_option = cfg.BoolOpt("ironic-inspector",
-                                       default=True,
+inspector_service_option = cfg.BoolOpt("ironic_inspector",
+                                       default=False,
                                        help="Whether or not ironic-inspector "
                                        "is expected to be available")