nss: preserve service name in getsrv call
    
    About case_sensitive=preserving and services.
    
    The name of the service can be preserved in
    result of 'getent service'. However we
    should still lowercase the protocol and
    service aliases because they serve as keys
    in some queries to sysdb. The lowercasing is done
    by the provider already. If we did not do that,
    we would lose case insesnsitivity.
    
    With this patch the responder preserves the
    case of service name and protocol, to match
    the case that is stored in the sysdb (however
    the protocol is already lowercased by provider,
    so it was done only for consistent use of the
    case_sensitive=preserve option in the responders
    and only the case of name is the same as in
    ldap).
    
    Fixes:
    https://fedorahosted.org/sssd/ticket/2460
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>