Remove install_resolv_conf from dib puppet script

This parameter is used for the unbound class, but we moved that class
out of openstack_project::template class and started managing unbound
here in the project-config dib elements, so we don't need to keep using
it and leaving it unset will not change any behavior.

Change-Id: I2ed1610dbfdc131943c64745e79da75133bf6818

nodepool/elements/puppet/bin/prepare-node

@@ -36,7 +36,6 @@ Service {
 }
 class {'openstack_project::single_use_slave':
   sudo => $SUDO,
-  install_resolv_conf => false,
   $puppet_ssh_key
 }
 EOF