Fix SI bug causing core dump sending to closed fd

The SIsendt function was not properly checking the file descriptor
and could core dump when an attempt was made to send on a connection
that was closed.

Issue-ID: RIC-207

Signed-off-by: E. Scott Daniels <daniels@research.att.com>
Change-Id: I09b33bf1185aef609bfff058b272e1895eb1a29d
3 files changed