Briefly delete manifested mapping type on a node without reason
When a dynamic type is introduced during indexing, the node that introduces it sends the fact that its added to the master, to be added to the master node. The master node then adds it to the index metadata and republishes that fact.

In order not to delete the mapping while the new type is introduced on the node that introduced it, we keep a map of seen mappings, and remove a mapping type when we already processed it.

The map is not properly cleared though in all places where an actual index service is being removed on a node.

closes #3697