Allow stat of /sys/module/lowmemorykiller files by system_server.

<5>[   43.929760] type=1400 audit(6342882.819:16): avc:  denied  { getattr } for  pid=779 comm="system_server" path="/sys/module/lowmemorykiller/parameters/adj" dev="sysfs" ino=6048 scontext=u:r:system_server:s0 tcontext=u:object_r:sysfs_lowmemorykiller:s0 tclass=file

Change-Id: I48828ca26814c6376c9c71c368f3eff0f7a8f219
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>