property_contexts

Resolves denials such as:
avc:  denied  { set } for property=ril.cdma.inecmmode scontext=u:r:radio:s0 tcontext=u:object_r:rild_prop:s0 tclass=property_service

This makes ril.cdma consistent with net.cdma.

We may ultimately need to coalesce rild_prop and radio_prop; they
were an attempt to distinguish what can be set by rild from what can be
set by com.android.phone, but the init property service DAC checking
permits any of them to be set by anything with the radio AID.  We
presently allow rild to set either type, but radio can only set radio_prop.

Change-Id: Ia3852db187e52427e18075e24b2beab19dd59c1f
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>