Use C vairant of YAML dumper at tasks serialization

To speed up seiralization time, use faster implementation of
YAML dumping when it is possible.

Change-Id: I992410328c07d14a1f5903aa91d456b040175a69
Partial-Bug: #1572103
Co-Authored-With: V. Kuklin <vkuklin@mirantis.com>
Co-Authored-With: B. Gaifullin <bgaifullin@mirantis.com>

nailgun/nailgun/db/sqlalchemy/models/mutable.py

@@ -243,3 +243,28 @@ yaml.add_representer(
     yaml.representer.SafeRepresenter.represent_list,
     yaml.Dumper
 )
+
+if yaml.__with_libyaml__:
+    yaml.add_representer(
+        MutableDict,
+        yaml.representer.SafeRepresenter.represent_dict,
+        yaml.CSafeDumper
+    )
+
+    yaml.add_representer(
+        MutableDict,
+        yaml.representer.SafeRepresenter.represent_dict,
+        yaml.CDumper
+    )
+
+    yaml.add_representer(
+        MutableList,
+        yaml.representer.SafeRepresenter.represent_list,
+        yaml.CSafeDumper
+    )
+
+    yaml.add_representer(
+        MutableList,
+        yaml.representer.SafeRepresenter.represent_list,
+        yaml.CDumper
+    )

nailgun/nailgun/yaql_ext/serializers.py

@@ -19,10 +19,16 @@ from yaql.language import specs
 from yaql.language import yaqltypes
 
 
+if yaml.__with_libyaml__:
+    YamlDumper = yaml.CSafeDumper
+else:
+    YamlDumper = yaml.SafeDumper
+
+
 @specs.method
 @specs.inject('finalizer', yaqltypes.Delegate('#finalize'))
 def to_yaml(finalizer, receiver):
-    return yaml.safe_dump(finalizer(receiver))
+    return yaml.dump_all([finalizer(receiver)], Dumper=YamlDumper)
 
 
 @specs.method