Fix hosts lists in example.pp
Fix hosts lists in example.pp

Using strings results in following errors:

Change-Id: I74e200a4c375830c18448bd60ccdd156d7b1c4d2
Error: join(): Requires array to work with at /etc/puppet/modules/trove/manifests/api.pp:352 on node XXX
Error: join(): Requires array to work with at /etc/puppet/modules/trove/manifests/api.pp:352 on node XXX

openstack/puppet-trove,openstack/puppet-trove,openstack/puppet-trove