Sepolicy: allow cnd to read tcp diagnostics

allow cnd to read tcp diagnostics through netlink socket
avc: denied { nlmsg_read } for pid=547 comm="cnd" scontext=u:r:cnd:s0
tcontext=u:r:cnd:s0 tclass=netlink_tcpdiag_socket permissive=0

Change-Id: I4c4241b475585f137313cf80935550b9650aea3c