use thread safe fnmatch

fnmatch is not thread safe in python <2.7.10, let's use the safe
one in oslo.utils

Change-Id: I09c8e25b584a253fa19c9f546188b419c2d5b35b
ref: https://hg.python.org/cpython/rev/fe12c34c39eb

heat/engine/environment.py

@@ -12,7 +12,6 @@
 #    under the License.
 
 import collections
-import fnmatch
 import glob
 import itertools
 import os.path
@@ -20,6 +19,7 @@ import re
 
 from oslo_config import cfg
 from oslo_log import log
+from oslo_utils import fnmatch
 import six
 
 from heat.common import environment_format as env_fmt