Add host_aggregates in exclude rule of audit scope

Currently if user wants to skip some host_aggregates from audit,
it is not possible. This patch adds host_aggregates into the exclude
rule of audit scope. This patch also implements audit-tag-vm-metadata
using scopes.

TODOs:
1. Add tests
2. Remove old implementation of audit-tag-vm-metadata

Change-Id: Ie86378cb02145a660bbf446eedb29dc311fa29d7
Implements: BP audit-tag-vm-metadata

watcher/api/controllers/v1/audit_template.py

@@ -109,6 +109,21 @@ class AuditTemplatePostType(wtypes.Base):
         common_utils.Draft4Validator(
             default.DefaultScope.DEFAULT_SCHEMA).validate(audit_template.scope)
 
+        include_host_aggregates = False
+        exclude_host_aggregates = False
+        for rule in audit_template.scope:
+            if 'host_aggregates' in rule:
+                include_host_aggregates = True
+            elif 'exclude' in rule:
+                for resource in rule['exclude']:
+                    if 'host_aggregates' in resource:
+                        exclude_host_aggregates = True
+        if include_host_aggregates and exclude_host_aggregates:
+            raise exception.Invalid(
+                message=_(
+                    "host_aggregates can't be "
+                    "included and excluded together"))
+
         if audit_template.strategy:
             available_strategies = objects.Strategy.list(
                 AuditTemplatePostType._ctx)