agent/lbaas: fix HAproxy package relationship

This patch fix this case:
- manage_haproxy_package is set to false
- puppetlabs-haproxy is not running
- we still want Neutron LBaaS working on the node
- we don't want at all the package managed by Puppet

Only set the dependency if the package is defined in the catalog.

Closes-bug #1340999
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>
Change-Id: Iee2211db8add4dfafba70706d69d1092339c6206
Merge "agent/lbaas: fix HAproxy package relationship"