Use travis_retry for farm tests (#7327)
Use travis_retry for farm tests (#7327)

* Use travis_retry in travis builds to retry the farm tests

* travis_retry is a bash function, so it can be called only from current bash

* Update .travis.yml

* Update .travis.yml

stweil/letsencrypt,lmcro/letsencrypt,letsencrypt/letsencrypt,stweil/letsencrypt,lmcro/letsencrypt,letsencrypt/letsencrypt