Fixed a bunch of typos throughout Neutron

Went through all of the docstrings in Neutron and did
some cleanup.  I'm sure there are bunch more that I have missed.

Change-Id: Ib29d2de1c580880c89ed4fd069e1515d0977a3e7
diff --git a/neutron/tests/tempest/common/credentials.py b/neutron/tests/tempest/common/credentials.py
index 9ae6ee8..9dfdff0 100644
--- a/neutron/tests/tempest/common/credentials.py
+++ b/neutron/tests/tempest/common/credentials.py
@@ -45,7 +45,7 @@
 
 # We want a helper function here to check and see if admin credentials
 # are available so we can do a single call from skip_checks if admin
-# creds area vailable.
+# creds are available.
 def is_admin_available():
     is_admin = True
     # If tenant isolation is enabled admin will be available