Add support for local boot

This patch implements the part that reads the specified boot_option in
the node.instance_info['capabilities'] that have been passed to Ironic by
the Nova Ironic Driver and pass that information to the deploy ramdisk
by adding it to the kernel cmdline in the PXE configuration file that
will be generated to that node.

This patch also makes sure that we clean the PXE configuration files for
the node marked to local boot after it's deployed, so that any attempt
to boot it from the network will not work.

This patch only apply to the pxe_* drivers, because the blueprint is
about adding local boot support for deployments that uses partition
images. The agent driver right now supports full disk images only.

Implements: blueprint local-boot-support-with-partition-images
Change-Id: Ide08e2b41dcf74c69dfbce242112da701fa15187

ironic/drivers/modules/deploy_utils.py

@@ -29,6 +29,7 @@ from oslo.utils import excutils
 from oslo.utils import units
 from oslo_concurrency import processutils
 from oslo_config import cfg
+from oslo_serialization import jsonutils
 import requests
 import six
 
@@ -677,3 +678,39 @@ def get_single_nic_with_vif_port_id(task):
     for port in task.ports:
         if port.extra.get('vif_port_id'):
             return port.address
+
+
+def parse_instance_info_capabilities(node):
+    """Parse the instance_info capabilities.
+
+    These capabilities are defined in the Flavor extra_spec and passed
+    to Ironic by the Nova Ironic driver.
+
+    NOTE: Although our API fully supports JSON fields, to maintain the
+    backward compatibility with Juno the Nova Ironic driver is sending
+    it as a string.
+
+    :param node: a single Node.
+    :raises: InvalidParameterValue if the capabilities string is not a
+             dictionary or is malformed.
+    :returns: A dictionary with the capabilities if found, otherwise an
+              empty dictionary.
+    """
+
+    def parse_error():
+        error_msg = (_("Error parsing capabilities from Node %s instance_info "
+                       "field. A dictionary or a dictionary string is "
+                       "expected.") % node.uuid)
+        raise exception.InvalidParameterValue(error_msg)
+
+    capabilities = node.instance_info.get('capabilities', {})
+    if isinstance(capabilities, six.string_types):
+        try:
+            capabilities = jsonutils.loads(capabilities)
+        except (ValueError, TypeError):
+            parse_error()
+
+    if not isinstance(capabilities, dict):
+        parse_error()
+
+    return capabilities