Note access right requirements for the job credential key files.

doc/html/quickstart.html

@@ -323,6 +323,8 @@ the program <a href="http://www.openssl.org">openssl</a>.
 An example of how to do this is shown below. 
 Specify file names that match the values of JobCredentialPrivateKey and 
 JobCredentialPublicCertificate in your configuration file.
+The JobCredentialPrivateKey file must be readable only by SlurmUser.
+The JobCredentialPublicCertificate file must be readable by all users.
 <pre>
 openssl genrsa -out /usr/local/etc/slurm.key 1024
 openssl rsa -in /usr/local/etc/slurm.key -pubout -out /usr/local/etc/slurm.cert