socket: don't attempt to reconnect a TCP socket in server mode

Commit c3767ed0eb5d0bb25fe409ae5dec06e3411ff1b6 introduced a possible SEGV when
using a socket chardev with server=on because it assumes that all TCP sockets
are in client mode.

This patch adds a check to only reconnect when in client mode.

Cc: Lei Li <lilei@linux.vnet.ibm.com>
Reported-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
