Fix typos for stack.sh and lib of comments and message

Fix 10 comments and 1 message

stack.sh
  Certicate => Certificate (comment)
lib/stack
  Sentinal => Sentinel (comment)
lib/neutron-legacy
  overriden => overridden (comment)
  necesssary => necessary (comment)
  notifiy => notify (message)
  notifations => notifications (comment)
lib/rpc_backend
  orginal => original (comment)
  cofiguration => configuration (comment)
lib/stack
  confgured => configured (comment)
lib/swift
  additinal => additional (comment)
  calclution => calculation (comment)
  maximun => maximum (comment)

Change-Id: I3637388b67decb007cd49af9addecc654009559b
diff --git a/stack.sh b/stack.sh
index 25c49c5..d3d3fb2 100755
--- a/stack.sh
+++ b/stack.sh
@@ -926,8 +926,8 @@
 restart_rpc_backend
 
 
-# Export Certicate Authority Bundle
-# ---------------------------------
+# Export Certificate Authority Bundle
+# -----------------------------------
 
 # If certificates were used and written to the SSL bundle file then these
 # should be exported so clients can validate their connections.