Auto merge of #3692 - malbarbo:test-args, r=alexcrichton
Auto merge of #3692 - malbarbo:test-args, r=alexcrichton

Pass multiples --test-args to the tester

Like --cfg, --test-args accept multiple matches, we should use it and
avoid some unexpected behavior joinning the arguments with space.

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