Do not allow stream socket retries in libkrad

Do not allow stream socket retries in libkrad

Before this patch, libkrad would follow the same exact logic for all
socket types when the retries parameter was non-zero.  This meant that
when connecting with SOCK_STREAM, multiple requests were sent in case
of packet drops, which, of course, cannot happen for SOCK_STREAM.

Instead, just disable retries for SOCK_STREAM sockets.

[ghudson@mit.edu: minor wording edits]

(cherry picked from commit 25e0656fdf9862faf9aa91288023776e9a47caad)

ticket: 8229
version_fixed: 1.13.3
status: resolved