Remove taskname from lowmemorykiller kill reports

Required because the lowmem_shrinker cannot use get_cmdline when called
from the direct reclaim path. Direct reclaim in do_page_fault() takes
mm->mmap_sem before calling shrinkers and get_cmdline also takes
mm->mmap_sem by calling access_process_vm. Userspace should be able to
recover taskname using the reported PID.

Bug: 130017100
Signed-off-by: Jim Blackler <jimblackler@google.com>
Test: Manually
Change-Id: I5f8b15bda60f9e2c0f6373ef54ad6fb95cda7a44