To make the local build environment more correct and consistent, we
should never leave an uncommitted go.mod in the tree; however, we need a
go.mod for certain commands to work properly. Use a wrapper script to
create and destroy the go.mod as needed instead of potentially changing
tooling behavior by leaving it.
If a go.mod already exists, this script will warn and call the wrapped
command with GO111MODULE=on.
Signed-off-by: Bjorn Neergaard <bneergaard@mirantis.com>