fixes RHEL/Centos/etc keystone service name ref

In the keystone install documentation, a service restart is performed
the doc currently uses service keystone, whereas the service name
is actually openstack-keystone not keystone.

fixes bug 1023435

Change-Id: I2b1d01608da01e4f4b588d2a31af3475512319e2

doc/src/docbkx/openstack-install/identity-install-keystone.xml

@@ -89,7 +89,7 @@
   <para>Next, restart the keystone service so that it picks up the new
     database configuration.</para>
   <screen os="ubuntu"><prompt>#</prompt> <userinput>sudo service keystone restart</userinput></screen>
-  <screen os="rhel;fedora;centos"><prompt>$</prompt> <userinput>sudo service keystone start &amp;&amp; sudo chkconfig keystone on</userinput></screen>
+  <screen os="rhel;fedora;centos"><prompt>$</prompt> <userinput>sudo service openstack-keystone start &amp;&amp; sudo chkconfig keystone on</userinput></screen>
   <para>Lastly, initialize the new keystone database, as root:</para>
   <screen><prompt>#</prompt> <userinput>keystone-manage db_sync</userinput></screen>
   <section xml:id="configure-keystone">