In busybox 1.30, the help of udhcpc for "-s" option changed:
--> busybox v1.27.2: -s,--script PROG	Run PROG at DHCP events (default /usr/share/udhcpc/default.script)
--> busybox v1.30.1: -s PROG		Run PROG at DHCP events (default /etc/udhcpc/default.script)
So, I changed the command line which extracts the script name to make it work for both versions
Signed-off-by: Rachid Koucha <rachid.koucha@gmail.com>