Install dnsmasq-utils on RedHat platforms

If $force_dhcp_release is true in nova.conf, nova tries to use the
tool "/usr/bin/dhcp_release", which isn't available without this
package. This ensures the package is present on RHEL-type systems.

See https://bugs.launchpad.net/nova/+bug/970893

Change-Id: I5470641410b4640e69ede19609e1f262e8cd0d3f