Lock testbed if failures are more than a threshold

This files needs to be used from Jenkins to lock the testbed
in case we see lot of failures

usage: stop_on_fail.py [-h] [-c FILE] [--files FILES [FILES ...]]
[--threshold THRESHOLD]

optional arguments:
-h, --help show this help message and exit
-c FILE, --conf_file FILE
Specify config file
--files FILES [FILES ...]
Files to be checked for test failed counts
--threshold THRESHOLD
Percentage of tests expected to be failed

Will checkin the corresponding contrail-tools chnages when this gets merged

Change-Id: I648959fedabbaed84791d04ed3818eeb8d5d481f