Improve test_baremetal_basic_ops

- test_baremetal_basic_ops now can test scenarios
for partition/wholedisk images.
- added a new configuration for tempest `boot_mode`.
- if boot_mode is uefi the test_baremetal_basic_ops
will run a verification to make sure the VM is using
uefi.

Change-Id: I920675b8a61a65c850b245283c3613b03f33ee6a
diff --git a/ironic_tempest_plugin/config.py b/ironic_tempest_plugin/config.py
index 95b29b3..90d55fc 100644
--- a/ironic_tempest_plugin/config.py
+++ b/ironic_tempest_plugin/config.py
@@ -150,6 +150,10 @@
                      "being used, this option should be set to True as "
                      "it lacks the needed components to make it locally "
                      "from a partition image."),
+    cfg.StrOpt('boot_mode',
+               default='bios',
+               choices=['bios', 'uefi'],
+               help="The desired boot_mode to be used on testing nodes."),
 ]
 
 BaremetalFeaturesGroup = [