Fix modelschema.schema_list()

* Fix glob path, since :
    ipdb> print '{}/*/*/schemas/*.yaml'.format(_get_base_dir())
    /usr/share/salt-formulas/env/*/*/schemas/*.yaml
    Process empty list:
    ipdb> print schemas
    []

Change-Id: I6ad048cb601baea9282e3c2a30fb79fdddd1ee0b

_modules/modelschema.py

 
     """
     output = {}
-    schemas = glob.glob('{}/*/*/schemas/*.yaml'.format(_get_base_dir()))
+    schemas = glob.glob('{}/*/schemas/*.yaml'.format(_get_base_dir()))
     for schema in schemas:
         if os.path.exists(schema):
             role_name = schema.split('/')[-1].replace('.yaml', '')