Install cython with the openstack-health api server

Pandas now has a build dep on cython. So to actually install an api
server now we need to ensure that cython is installed on the machine.
This commit adds that to api.pp manifest.

Change-Id: I55053b4c5d7d6edde191fd0c695d446dc216bcba

manifests/api.pp

@@ -105,11 +105,16 @@ class openstack_health::api(
     ensure => present,
   }
 
+  package {'cython':
+    ensure => present,
+  }
+
   exec { 'requirements':
     command     => "${virtualenv_dir}/bin/pip install -U -r ${source_dir}/requirements.txt",
     require     => [
       Python::Virtualenv[$virtualenv_dir],
       Package['libmemcached-dev'],
+      Package['cython'],
     ],
     subscribe   => Vcsrepo[$source_dir],
     refreshonly => true,