Generalize rmnet entry for radio properties.

Our policy also has this entry:
net.rmnet_usb0.         u:object_r:radio_prop:s0

Rather than trying to enumerate all possible variants, just reduce
the existing rmnet0 entry to rmnet so that it matches all properties
with that prefix.

Change-Id: Ic2090ea55282fb219eab54c96fd52da96bb18917
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>

property_contexts

@@ -2,7 +2,7 @@
 # property service keys
 #
 #
-net.rmnet0              u:object_r:radio_prop:s0
+net.rmnet               u:object_r:radio_prop:s0
 net.gprs                u:object_r:radio_prop:s0
 net.ppp                 u:object_r:radio_prop:s0
 net.qmi                 u:object_r:radio_prop:s0