oe-selftest: optimize code in _sstatetests_noauto.py module
1) Some of the checks made when creating new directories are unnecessary beacause
the test will fail anyway if os.mkdir() fails, with the appropriate error message.
Removing this code.
2) Moved the adding to tracked paths for deletion of temporary build directories
and sstate-cache directories to after they are created. This makes more sense
and prevents deletion of these directories if they allready exist and may contain
useful data.
Signed-off-by: Corneliu Stoicescu <corneliux.stoicescu@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
