twister: better handling of error reporting

Stop counting errors as failures and report them as is. This fixes
issues with counting when retrying failures and errors.
We have been adding errors to failures and then double count them when
displaying information on the screen instead of keep an accurate count
in the counter class.

This is now fixed and we do report errors seperately, ie. build errors.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>