getbootparam returns the wrong parameter if option name is a substring of
another option

Attached patch should fix this.

example:

[~ ] -> source /etc/grml/autoconfig.functions
[~ ] -> export CMDLINE='apm=power-off vga=791 quiet
initrd=/boot/grmldailysid/initrd.gz boot=live nomce  noeject ssh=grml noprompt
noquick config scripts=/live/image/unp.sh netconfig=192.168.0.1/config.tbz'
[~ ] -> getbootparam config                  
apm=power-off