lowmemorykiller: Run the lowmemory notifier when killing

When the lowmemory killer starts killing processes, it's useful to
be able to see the state of other memory in the system. Call the
lowmemory notifier to get other clients to dump out their state.

Change-Id: Ie3b1d47149f0108b42b7961fd47a8cc5efe2c590
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>