Fixed some typos in the doc

doc/cta.tex

@@ -320,7 +320,7 @@ fstofs.broker root://devbox.cern.ch:1097//eos/
   sudo service eos start
 \end{verbatim}
 
-\subsection{Enable the kerboos and simple shared secret authentication mechanisms within EOS as opposed to xroot}
+\subsection{Enable the kerberos and simple shared secret authentication mechanisms within EOS as opposed to xroot}
 \begin{verbatim}
   sudo eos vid enable sss
   sudo eos vid enable krb5
@@ -610,7 +610,7 @@ RMCD_OPTIONS=/dev/smc
 \end{boxedverbatim}
 
 \section{Starting up the xroot server with the CTA plugin}
-Before starting the xroot server we need to change the VFS backend permissions again (because new files have been created with the \texttt{stage:st} user). Example:
+Before starting the xroot server we need to change the VFS backend permissions again (because new files have been created with the \texttt{stage:st} user by the tapeserver daemon). Example:
 
 \begin{verbatim}
   $ chmod -R 0777 /tmp/jobStoreVFSOKJCjW