Modify some spelling mistakes

There are some comment errors, it's modify 'Captial' to 'Capital' in
keystone file, and modify 'possition' to 'position' in openrc file, and
modify 'comming' to 'coming' in stack file, and
modify 'prefered' to 'preferred' in stackrc file.

Change-Id: I0fdd539cbfff842a4ba7fca9100b881443300f9a
diff --git a/stackrc b/stackrc
index 877da82..b03426f 100644
--- a/stackrc
+++ b/stackrc
@@ -80,7 +80,7 @@
 # CELLSV2_SETUP - how we should configure services with cells v2
 #
 # - superconductor - this is one conductor for the api services, and
-#   one per cell managing the compute services. This is prefered
+#   one per cell managing the compute services. This is preferred
 # - singleconductor - this is one conductor for the whole deployment,
 #   this is not recommended, and will be removed in the future.
 CELLSV2_SETUP=${CELLSV2_SETUP:-"superconductor"}
@@ -117,7 +117,7 @@
 # Whether or not to enable Kernel Samepage Merging (KSM) if available.
 # This allows programs that mark their memory as mergeable to share
 # memory pages if they are identical. This is particularly useful with
-# libvirt backends. This reduces memory useage at the cost of CPU overhead
+# libvirt backends. This reduces memory usage at the cost of CPU overhead
 # to scan memory. We default to enabling it because we tend to be more
 # memory constrained than CPU bound.
 ENABLE_KSM=$(trueorfalse True ENABLE_KSM)