Fixed LD_PRELOAD issue

Well, this means that `LD_PRELOAD` cant find the library `libsigchain.so` (is and android lib so we dont need it here * i think) , this happends because `LD_PRELOAD` (a enviroment var) is inherited from the  android enviroment.

The lib `libsigchain.so` is located at `/system/lib/` (from phone root)

So, if we add the next line to bootkali && killkali:

     unset LD_PRELOAD

 Errors gone.
 
 Jaime