When using cargo in unit tests, its temporary files need to be cleaned up

Unit tests that use cargo is causing issues when a build machine is used by multiple people.

The error is caused by the permission of /tmp/cargo/con/cargocpc.war which is owned by previous person doing the build.
The workaround is to do 'su - &&rm -rf /tmp/cargo'

Can the unit tests be updated to clean out the /tmp/cargo directory?