Allow dnsmasq to inherit/use netd UDP socket.

Addresses denials such as:
avc: denied { read write } for comm="dnsmasq" path="socket:[1054090]" dev="sockfs" ino=1054090 scontext=u:r:dnsmasq:s0 tcontext=u:r:netd:s0 tclass=udp_socket
This may not be needed (need to check netd to see if it should be closing
all of these sockets before exec'ing other programs), but should be harmless.

Change-Id: I77c7af5e050e039fd48322914eeabbcb8a716040
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>