Making fetch to work with file on sub dir on tftp server.

This patch allows live-initramfs to fetch file from sub
dir on tftp server. The original one from live-initramfs 1.157.2 only
works for the file existing on the root of tftp server, e.g.
fetch=tftp://192.168.101.254/filesystem.squashfs

It allows the PXE client to get the file either on the root, or on
the sub dir, e.g. fetch=tftp://192.168.101.254/live/filesystem.squashfs
is working now.

scripts/live

@@ -773,9 +773,11 @@ do_httpmount ()
 					then
 						case "$url" in
 							tftp*)
-								ip="$(dirname $url | sed -e 's|tftp://||g')"
-								log_begin_msg "Trying tftp -g -b 10240 -r $(basename ${url})  -l ${dest}/$(basename ${url}) $ip"
-								tftp -g -b 10240 -r $(basename ${url})  -l ${dest}/$(basename ${url}) $ip
+								ip="$(dirname $url | sed -e 's|tftp://||g' -e 's|/.*$||g')"
+								rfile="$(echo $url | sed -e "s|tftp://$ip||g")"
+								lfile="$(basename $url)"
+								log_begin_msg "Trying tftp -g -b 10240 -r $rfile -l ${dest}/$lfile $ip"
+								tftp -g -b 10240 -r $rfile -l ${dest}/$lfile $ip
 							;;
 
 							*)