The time period between getting pid
of haproxy service and checking existance of
pid file is very short, if with in this period
haproxy service get reload then the race condition
occured and container get exit as extend_start.sh
script exit.

To minimize the risk of race condition, this patch
let the extend_start.sh script to try upto 3 times
before exit.

Closes-Bug: #1479888

Change-Id: I2f9b7ec832dec8d94a2cdd27ca8a212d0c65a60d