mongodb/hiera: node_ip isn't an array

[Emilien Macchi]

Since https://github.com/voxpupuli/puppet-mongodb/commit/23068c10a41b5f696ed9d6077d6c633c71e519fc

node_ip has to be an array or we get this error:

Oct 23 01:39:51 localhost os-collect-config: "Error: Evaluation Error: Error while evaluating a Function Call, Class[Mongodb::Server]: parameter 'bind_ip' expects an Array value, got String at /etc/puppet/modules/tripleo/manifests/profile/base/database/mongodb.pp:47:5 on node centos-7-citycloud-lon1-0000374920.localdomain",

http://logs.openstack.org/60/513760/2/check/legacy-tripleo-ci-centos-7-scenario002-multinode-oooq-puppet/50e7033/logs/subnode-2/var/log/messages.txt.gz#_Oct_23_01_39_51