Skip connection-timeout when missing FD passing.

This tests uses multiplexing which uses file descriptor passing, so
skip it if we don't have that.  Fixes test failures on Cygwin.

Author: daztucker

regress/connection-timeout.sh

@@ -2,6 +2,9 @@
 #	Placed in the Public Domain.
 
 tid="unused connection timeout"
+if config_defined DISABLE_FD_PASSING ; then
+       skip "not supported on this platform"
+fi
 
 CTL=$OBJ/ctl-sock
 cp $OBJ/sshd_proxy $OBJ/sshd_proxy.orig