kola/tests: fix a bunch of race conditions in files tests
kola/tests: fix a bunch of race conditions in files tests

The tests are checking if files exist with problematic modes, so we
don't care about them if they are deleted before stat is called.

quantum/coreos-mantle,glevand/coreos--mantle,dm0-/mantle,glevand/coreos--mantle,marineam/mantle,marineam/mantle,dm0-/mantle,quantum/coreos-mantle