Grant CAP_SYS_NICE to processes that need it.

New binder kernel changes extend the areas where
binder will set real-time scheduling priorities
on threads; to make sure the driver can correctly
determine whether a process is allowed to run
at real-time priority or not, add the capability
to the services that need it.

Bug: 37293077
Test: processes run at real-time prio on incoming
      real-time binder calls.

Change-Id: Ia4b3e5ecb1f5e18e7272bdaaad5c31a856719633