Incorporate hotplugd(8) patches from the OpenBSD port

https://cvsweb.openbsd.org/~checkout~/ports/graphics/sane-backends/patches/patch-tools_openbsd_attach?rev=1.3
https://cvsweb.openbsd.org/~checkout~/ports/graphics/sane-backends/patches/patch-tools_openbsd_detach?rev=1.2

While there, use "$()" instead of "``" for running commands in a
subshell (this is to match `attach` change commited earlier).

More whitespace fixes.

tools/openbsd/attach

@@ -11,8 +11,8 @@ case $DEVCLASS in
 		BUSNAME=$(usbdevs -vv | egrep "Controller|$DEVNAME\$" | grep -B 1 "$DEVNAME\$" | awk -F'[ :]' '/^Controller/ { print $2 }')
 		echo $BUSNAME > /var/run/${DEVNAME}.bus
 		# probably our scanner
-		chgrp usb /dev/"$DEVNAME".*
-		chgrp usb /dev/"$BUSNAME"
+		chown _cups:_saned /dev/"$DEVNAME".*
+		chown _cups:_saned /dev/"$BUSNAME"
 		;;
 	esac
 	;;

tools/openbsd/detach

@@ -8,15 +8,14 @@ case $DEVCLASS in
 	# generic devices
 	case "$DEVNAME" in
 	ugen*)
-		BUSNAME=`cat /var/run/${DEVNAME}.bus`
+		BUSNAME=$(cat /var/run/${DEVNAME}.bus)
 		rm -f /var/run/${DEVNAME}.bus
 		# probably our scanner
 		chgrp wheel /dev/"$DEVNAME".*
 		if [ x$BUSNAME != x ] ; then
-			chgrp wheel /dev/"$BUSNAME"
+			chown root:wheel /dev/"$BUSNAME"
 		fi
 		;;
 	esac
-
-        ;;
+	;;
 esac