Allow dnsmasq dac_override capability.

dnsmasq presently requires dac_override to create files under
/data/misc/dhcp.  Until it can be changed to run with group dhcp,
allow dac_override.

Addresses denials such as:
avc:  denied  { dac_override } for  pid=21166 comm="dnsmasq" capability=1  scontext=u:r:dnsmasq:s0 tcontext=u:r:dnsmasq:s0 tclass=capability

Change-Id: Ic352dc7fc4ab44086c6b06cf727c48f29098f3a1
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>