tuna: remove the discard option in init.d/98SONIC_SHOCK

google now trims writable partitions once week, thus no need for discard anymore

Change-Id: I8779a442787606640edb9c428fff5ce7d7a095f7
Signed-off-by: Dan Trifan <jimsth@gmail.com>
Merge "tuna: remove the discard option in init.d/98SONIC_SHOCK" into jb43