Nova now requires an api database to be created

This enables the creation of the nova_api database that is now
mandatory since https://review.openstack.org/#/c/245828/

Change-Id: I8c8530e7711891d3de3bf0b25fe0c8ecb4e8b028
Related-Bug: #1539793

packstack/modules/ospluginutils.py

@@ -45,6 +45,14 @@ class ManifestFiles(object):
 
         self.filelist.append((filename, marker))
 
+    def prependFile(self, filename, marker, data=''):
+        self.data[filename] = data + '\n' + self.data.get(filename, '')
+        for f, p in self.filelist:
+            if f == filename:
+                return
+
+        self.filelist.append((filename, marker))
+
     def getFiles(self):
         return [f for f in self.filelist]
 
@@ -76,6 +84,10 @@ def appendManifestFile(manifest_name, data, marker=''):
     manifestfiles.addFile(manifest_name, marker, data)
 
 
+def prependManifestFile(manifest_name, data, marker=''):
+    manifestfiles.prependFile(manifest_name, marker, data)
+
+
 def generateHieraDataFile():
     os.mkdir(basedefs.HIERADATA_DIR, 0o700)
     with open(HIERA_DEFAULTS_YAML, 'w') as outfile: