Add an exception for bluetooth to the sysfs neverallow rule.

This is required for the grouper sepolicy, where we must allow
bluetooth domain to write to the base sysfs type due to a kernel bug.

Change-Id: I14b0530387edce1097387223f0def9b59e4292e0
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>