Make sure the return value of by_file_ctrl(..., X509_L_FILE_LOAD, ...)

aka X509_LOOKUP_load_file(...) is always 0 or 1, not the counter
returned from the recently introduced function X509_load_cert_crl_file.
X509_STORE_load_locations expects X509_LOOKUP_load_file to return 1 on
success, and possibly there's other software that relies on this too.