Don't try to set service.bootanim.exit

init has never allowed the bootanimation code to
set service.bootanim.exit, and has always generated the
dmesg error message

  <3>[   17.644615] init: sys_prop: permission denied uid:1003  name:service.bootanim.exit

Since setting this property has no effect and never worked, delete
the code which tries to do it.

Change-Id: Idacc5467d85479a8cf974702af8895011be585ea