Auto merge of #3785 - joshtriplett:insulate-tests-from-user-env, r=alexcrichton
Auto merge of #3785 - joshtriplett:insulate-tests-from-user-env, r=alexcrichton

tests: Insulate from user git environment

Several tests in "cargo test" would fail if the user had any of the Git
environment variables set for name or email address, because those
environment variables would override the tested configuration.  Filter
out those environment variables.

rust-lang/cargo,rustyhorde/cargo,achanda/cargo,tshepang/cargo,nipunn1313/cargo,durka/cargo,tsurai/cargo,rustyhorde/cargo,vojtechkral/cargo,vojtechkral/cargo,tshepang/cargo,rustyhorde/cargo,achanda/cargo,tsurai/cargo,eminence/cargo,achanda/cargo,rust-lang/cargo,tshepang/cargo,vojtechkral/cargo,tsurai/cargo,durka/cargo,durka/cargo,eminence/cargo,achanda/cargo,durka/cargo,nipunn1313/cargo,rustyhorde/cargo,eminence/cargo,tsurai/cargo,nipunn1313/cargo,vojtechkral/cargo,rust-lang/cargo,eminence/cargo,rust-lang/cargo,nipunn1313/cargo,tsurai/cargo,tshepang/cargo