SELinux: Add system group to thermald to avoid dac_override denial.

Change helps resolve the following denial.

avc:  denied  { dac_override } for  pid=441 comm="thermald" capability=1  scontext=u:r:thermald:s0 tcontext=u:r:thermald:s0 tclass=capability

A similar change already exists for the hammerhead policy. Future
changes might need to be added here to accommodate additional
dac_override denials that might happen beyond this change. Consult
hammerhead change Ied2293d9effb1b2d9e043e01c08b5e7be407c868 for
some additional insight.

Conflicts:
	init.flo.rc

Change-Id: Ica6d657e5c37851b725f0b2bbe6b46d18ceb84bb
Signed-off-by: rpcraig <rpcraig@tycho.ncsc.mil>