Added count percolate api

Added a new percolate api that only returns the number of percolate queries that have matched with the document being percolated. The actual query ids are not included. The percolate total count will be put in the total field and is the only result that will be returned from the dedicated count apis.

The total field will also be included in the already existing percolate and percolating existing document apis and are equal to the number of matches.

Closes #3430
Use debug logging rather than info for rejected ping task

This exception is thrown on node shutdown and doesn't indicate
an critical situation but rather is caught for consistency reasons.