Fix typo errors in devstack documentation

This submission fixes typo errors in following files
  1. contributing.rst
  2. exerciserc.rst
  3. faq.rst
  4. local.conf.rst
  5. openrc.rst

Change-Id: I2b2d61673c3c95f60c56978b5a81016603fef252
diff --git a/doc/source/contributing.rst b/doc/source/contributing.rst
index 8c9e658..b2a219b 100644
--- a/doc/source/contributing.rst
+++ b/doc/source/contributing.rst
@@ -5,7 +5,7 @@
 DevStack uses the standard OpenStack contribution process as outlined in
 `the OpenStack wiki 'How To
 Contribute' <https://wiki.openstack.org/wiki/How_To_Contribute>`__. This
-means that you will need to meet the requirements of the Contribututors
+means that you will need to meet the requirements of the Contributors
 License Agreement (CLA). If you have already done that for another
 OpenStack project you are good to go.