tcp_wrapper: Clean up logit()

Eliminate these compiler warnings:

tcpwrapper.c: In function logit
tcpwrapper.c:225: warning: unused parameter procnum
tcpwrapper.c:225: warning: unused parameter prognum

Actually, @procnum is not used anywhere in our tcpwrapper.c, so
let's just get rid of it.

Since there is only one logit() call site in tcpwrapper.c, the macro
wrapper just adds needless clutter.  Let's get rid of that too.

Finally, both mountd and statd now use xlog(), which adds an
appropriate program name prefix to every message.  Replace the
open-coded syslog(2) call with an xlog() call in order to
consistently identify the RPC service reporting the intrusion.

Since logit() no longer references "deny_severity" and no nfs-utils
caller sets either allow_severity or deny_severity, we remove them.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Steve Dickson <steved@redhat.com>