Only run Travis on master branch, not on export-DXXXXX branches. (#16628)
Summary:
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/16628
Differential Revision: D13922097
Pulled By: ezyang
fbshipit-source-id: eb16d90cc61167af5edc0c4e361d7a807a3099e5
