tests: try to force remove higher minor first

tests: try to force remove higher minor first

When force removing thin-pool we loose 'real' access to hidden device,
and if such pool is in suspended state, any thin volume cannot be
dropped. It likely should be also checked by dmsetup, but meanwhile
apply simple logic -  try to force remove first all higher minors first
with assumption we first create thin-pool and then thin volume
and there are usually not being released lower dm numbers to
get the order wrong.