statd: squelch compiler warning in sm-notify.c

Clean up:  Get rid of a false positive compiler warning, seen with
-Wextra.

sm-notify.c: In function ¿record_pid¿:
sm-notify.c:690: warning: comparison between signed and unsigned integer
expressions

Document some ignored return codes while we're here.

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