devstack: Adding a README for ironic-bm-logs directory

Adding a README file to be put into the ironic-bm-logs/ directory that
explains the virtual bare-metal log files.

Change-Id: If4fc6b53273d39c65db0251957795d214440118d

devstack/lib/ironic

@@ -1254,6 +1254,30 @@ function setup_qemu_log_hook {
     " -i $IRONIC_LIBVIRT_HOOKS_PATH/qemu
 
     restart_libvirt
+    mkdir -p $IRONIC_VM_LOG_DIR
+    cat >${IRONIC_VM_LOG_DIR}/README << EOF
+This directory contains the serial console log files from the virtual Ironic
+bare-metal nodes. The *_console_* log files are the original log files and
+include ANSI control codes which can make the output difficult to read. The
+*_no_ansi_* log files have had ANSI control codes removed from the file and are
+easier to read.
+
+On some occasions there won't be a corresponding *_no_ansi_* log file, for
+example if the job failed due to a time-out. You may see a log file without a
+date/time in the file name. In that case you can display the logfile in your
+console by doing:
+   $ curl URL_TO_LOGFILE
+
+This will have your terminal process the ANSI escape codes.
+
+Another option, if you have the 'pv' executable installed, is to simulate a
+low-speed connection.  In this example simulate a 300 Bytes/second connection.
+   $ curl URL_TO_LOGFILE | pv -q -L 300
+
+This can allow you to see some of the content before the screen is cleared by
+an ANSI escape sequence.
+
+EOF
 }
 
 function create_bridge_and_vms {