abrt-ccpp: try to read hs_err.log from crash's CWD

- it is expected that this may fail in some particular cases but the
  failure is not critical a the hook will pass it

- closes #622

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>