When an exec directory is shared between services, this allows one of the
service to be the producer of files, and the other the consumer, without
letting the consumer modify the shared files.
This will be especially useful in conjunction with id-mapped exec directories
so that fully sandboxed services can share directories in one direction, safely.
Having these named differently than the test itself mostly creates
unecessary confusion and makes writing logic against the tests harder
so let's rename the testsuite-xx units and scripts to just use the
test name itself.