Remove remnants of Windows support in system test

The "uname -o" command is harmful on OpenBSD because this platform does
not know about the "-o" option. It is a permanent failure since system
tests are started with "set -e".

bin/tests/system/ifconfig.sh.in

@@ -123,10 +123,6 @@ up() {
 		[ "$a" ] && ifconfig lo0 alias $a
 		[ "$aaaa" ] && ifconfig lo0 inet6 $aaaa alias
 		;;
-	    *-cygwin*)
-		echo "Please run ifconfig.bat as Administrator."
-		exit 1
-		;;
 	    *)
 		echo "Don't know how to set up interface.  Giving up."
 		exit 1
@@ -211,10 +207,6 @@ down() {
 		[ "$a" ] && ifconfig lo0 -alias $a
 		[ "$aaaa" ] && ifconfig lo0 inet6 $aaaa delete
 		;;
-	    *-cygwin*)
-		echo "Please run ifconfig.bat as Administrator."
-		exit 1
-		;;
 	    *)
 		echo "Don't know how to destroy interface.  Giving up."
 		exit 1