nss: allow UPNs in SSS_NSS_GETSIDBYNAME and SSS_NSS_GETORIGBYNAME
When adding support for UPNs, email addresses and aliases the
SSS_NSS_GETSIDBYNAME and SSS_NSS_GETORIGBYNAME request were forgotten.
This patch adds the missing support because it might be irritating if
getpwnam() can resolve the name but the other requests fail. The same
logic as for the plain user lookup is used, this add some code
duplication which is expected to be removed when the nss responder will
be switched to use the new cache_req code.
Reviewed-by: Jakub Hrozek <firstname.lastname@example.org>