Allow clatd CAP_IPC_LOCK for mmap()

clatd's environment may not have a sufficiently large memlock
ulimit; it needs >=1MB but values much lower can be encountered.

The mmap() is performed while clatd is still root, before dropping
privileges; allow this to succeed.

Bug: 21736319
Change-Id: I8171e077046566924c769e855144ae5fac634d4c