Highlight mknb failure on upgrade

If for example the filesystem fills, a more obvious message
should be presented.

xCAT/xCAT.spec

@@ -241,6 +241,8 @@ fi
 mkdir -p /var/log/xcat
 date >> /var/log/xcat/upgrade.log
 $RPM_INSTALL_PREFIX0/sbin/xcatconfig -u -V >> /var/log/xcat/upgrade.log
+if grep "Failed to copy  /opt/xcat/share/xcat/netboot/genesis/x86_64/fs" /var/log/xcat/upgrade.log; then
+    echo 'mknb failed to complete successfully'
 fi
 exit 0