Fixes README.md on APACHE_ENABLED_SERVICES=keystone

The documentation stated that, to enable Keystone running on Apache,
one should set:
APACHE_ENABLED_SERVICES+=keystone,swift

However, it actually works with:
APACHE_ENABLED_SERVICES+=key,swift

Change-Id: I8cc92e9426d7fc3117b30df01babdb50576328af
Closes-bug: #1311461
diff --git a/README.md b/README.md
index 89e3855..f9a996e 100644
--- a/README.md
+++ b/README.md
@@ -124,7 +124,7 @@
 `APACHE_ENABLED_SERVICES` in your ``localrc`` section.  Remember to
 enable these services at first as above.
 
-    APACHE_ENABLED_SERVICES+=keystone,swift
+    APACHE_ENABLED_SERVICES+=key,swift
 
 # Swift