speedup the cleanup after testcases deleting pods in separate
goroutines.
The post-test cleanup stage must be done carefully since pod require
exclusive allocation - so pods must take all the steps to properly
cleanup the tests to avoid to pollute the environment, but
this has a negative effect on test duration (take longer).
Hence, we add safe speedups like doing pod deletions in parallel.
Signed-off-by: Francesco Romani <fromani@redhat.com>
adfff27279