Use correct bit when writing PIV certificate object with gzipped certificate

NIST 800-73 clarified the CertInfo flag for gzipped certificate is 0x01
piv-tool was writting 0x80.
OpenSC card-piv.c continues to accept both.
Merge pull request #324 from dengert/piv-gzip-cert

Use correct bit when writing PIV certificate object with gzipped certifi...