Enable boot_option to be specified

The ability to set this is required as some test cases do not
support a duality of local boot and network boot when using
the cirros test image. This is because cirros lacks the tools
to install a grub2 boot loader.

Adds a ``[baremetal]partition_netboot`` configuration parameter
which defaults to ``True``. This allows a test executor to tell
the tests if we should expect to network boot all partition
image usage. This is ultimately required to enable ironic to
change the underlying default boot_option netboot to local.

Story: #1619339

Change-Id: I784d5c9d98d574fc1f00dd8f5ee1e20499bf2e34
diff --git a/ironic_tempest_plugin/config.py b/ironic_tempest_plugin/config.py
index d5cdcfa..d232790 100644
--- a/ironic_tempest_plugin/config.py
+++ b/ironic_tempest_plugin/config.py
@@ -143,7 +143,14 @@
                     "as instance_info/root_gb value."),
     cfg.IntOpt('available_nodes', min=0, default=None,
                help="The number of baremetal hosts available to use for "
-                    "the tests.")
+                    "the tests."),
+    cfg.BoolOpt('partition_netboot',
+                default=True,
+                help="Treat partition images as netbooted as opposed to "
+                     "attempting to populate a boot loader. IF cirros is "
+                     "being used, this option should be set to True as "
+                     "it lacks the needed components to make it locally "
+                     "from a partition image."),
 ]
 
 BaremetalFeaturesGroup = [