Remove filter as test which is going to be deprecated

[jordiclariana]

With Ansible 2.6 this warning is shown:

[DEPRECATION WARNING]: Using tests as filters is deprecated. Instead of using `result|version_compare` use `result 
is version_compare`. This feature will be removed in version 2.9. Deprecation warnings can be disabled by setting 
deprecation_warnings=False in ansible.cfg.

This PR fixes this.

[ernestas-poskus]

Then we will have to bump required Ansible version https://github.com/AnsibleShipyard/ansible-zookeeper/blob/master/meta/main.yml#L7

[jordiclariana]

I don't think that is necessary. I made this change here too and I checked against Ansible 2.2 and it worked perfectly, so I think is safe to say it is backwards compatible until Ansible 2.2 at least.