Prefer .gitconfig username
Prefer .gitconfig username

We should check first the .gitconfig username and then the
environment variables. Otherwise, the .gitconfig username is never
used.

Bug: #1223676
Change-Id: I3b7efd53e1e561108b42a471ddcebfd87984922b

meelapshah/git-review,ka2m/git-review,meelapshah/git-review,openstack-infra/git-review,entropia1/git-review,jeeloo/git-review