Update dist-sort module for better effectiveness

The dist-sort module has been updated to ensure its execution
is effective, fast, and nonintrusive. There are cases where
the rounds made by the module take an excessive amount of time
to complete. This change ensures that the module is limiting its
rounds to a known index and the iterable is processed using a
generator.

Change-Id: I03d1f70cb6cd17f38ef37b4d8371a8982beca29e
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

library/dist_sort

@@ -15,9 +15,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+
 # import module snippets
 from ansible.module_utils.basic import *
 
+
 DOCUMENTATION = """
 ---
 module: dist_sort
@@ -60,6 +62,7 @@ author:
   - Sam Yaple
 """
 
+
 EXAMPLES = """
 - dist_sort:
     value_to_lookup: "Hostname-in-ansible-group_name"
@@ -106,15 +109,18 @@ class DistSort(object):
 
         :returns: ``str``
         """
-        index = self.params['ref_list'].index(self.params['value_to_lookup'])
-        index += self.params['sort_modifier']
-        src_list = self.params['src_list'].split(
-            self.params['delimiter']
+        try:
+            index = self.params['ref_list'].index(
+                self.params['value_to_lookup']
             )
+        except ValueError:
+            index = 0
 
-        for _ in range(index % len(src_list)):
+        src_list = self.params['src_list'].split(self.params['delimiter'])
+        index += self.params['sort_modifier']
+        for _ in xrange(index % len(src_list)):
             src_list.append(src_list.pop(0))
-        else:
+
         return self.params['delimiter'].join(src_list)
 
 
@@ -151,18 +157,17 @@ def main():
         # This is done so that the failure can be parsed and does not cause
         # ansible to fail if a non-int is passed.
         module.params['sort_modifier'] = int(module.params['sort_modifier'])
-
         _ds = DistSort(module=module)
         if _ds.return_data == module.params['src_list']:
             _changed = False
         else:
             _changed = True
-
-        module.exit_json(changed=_changed, **{'sorted_list': _ds.return_data})
     except Exception as exp:
         resp = {'stderr': str(exp)}
         resp.update(module.params)
         module.fail_json(msg='Failed Process', **resp)
+    else:
+        module.exit_json(changed=_changed, **{'sorted_list': _ds.return_data})
 
 if __name__ == '__main__':
     main()