Fix github hook to actually trigger on changes to master.
Fix github hook to actually trigger on changes to master.

Change-Id: If24e87d5037fb1cad7efae7da94c20da281e5eca

bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration