Report elapsed time during cron runs

Give a simple report how long it took to run full cron.

Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>

peebz/command.py

diff --git a/peebz/command.py b/peebz/command.py
index a7cb2f7..7b6dc16 100644
--- a/peebz/command.py
+++ b/peebz/command.py
@@ -6,6 +6,8 @@
 
 import sys
 import argparse
+import time
+
 import b4
 import logging
 import logging.handlers
@@ -35,12 +37,16 @@
 
 
 def cmd_cron(cmdargs):
+    cstart = int(time.time())
+    logger.info('--- Start cron ---')
     logger.info('--- Running bz2pi ---')
     cmd_bz2pi(cmdargs)
     logger.info('--- Running pi2bz ---')
     cmd_pi2bz(cmdargs)
     logger.info('--- Running git2bz ---')
     cmd_git2bz(cmdargs)
+    celapsed = int(time.time()) - cstart
+    logger.info('--- End cron (elapsed: %s s) ---', celapsed)
 
 
 def cmd_bzdump(cmdargs):