Require all additional remote refs to be given explicitly in git_branch_poller
Require all additional remote refs to be given explicitly in git_branch_poller

git remote add <remote> puts a default entry for remote.<remote>.fetch: +refs/heads/*:refs/remotes/<remote>/*. Unset it before adding additional entries.

BUG=491246

Review URL: https://codereview.chromium.org/1159983004

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@295436 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build