filter NaN values

Change-Id: I77fbe804b5b48107722e1db15ce07d211a600402
Reviewed-on: http://review.couchbase.org/25203
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>
track rebalance progress even if it's not running

Change-Id: I3cd5c2a58b3aa1c27c19f1907a798c96f2925e87
Reviewed-on: http://review.couchbase.org/25204
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>