Return proper tox exit code
Return proper tox exit code

Change-Id: I4e27a27e40a517c2244807424ba4d5ca97cd3e69
Signed-off-by: Walinton Cambronero <1f04f885082cc0892df9219a8132f4f8086a7db5@hpe.com>

open-switch/infra_project-config,open-switch/infra_project-config