Just Pushed: Expected nodes setting in gateway recovery


Stemmed from a discussion I had with /ask a couple of mails back in the
mailing list, I added the following feature:
http://github.com/elasticsearch/elasticsearch/issues/issue/404. Here is the
desc in the feature:

Currently, one can set gateway.recover_after_nodes setting to control after
how many nodes within the cluster recovery will start. The
gateway.recover_after_time sets the time to wait till recovery happens once
the nodes are met.

The missing setting in this scenario is the ability to set how many nodes
are "expected" to be in the cluster. For example, setting:

recover_after_nodes: 1
recover_after_time: 5m
expected_nodes: 2

In an expected 2 nodes cluster will cause recovery to start 5 minutes after
the first node is up, but once there are 2 nodes in the cluster, recovery
will begin immediately (without waiting).