Support nodes with launch condition Some special nodes when started from an image will not be instantly available, they might be busy for a while. Nodepool should wait, until the nodes are ready. An ssh connection is established to the node and the node is considered to be ready when a given file has been found on the filesystem of the node. Was I67fd9b92e838f8dfc1a4d17bef0390677e36591c (abandoned) Change-Id: Idc0981c06f9092324362fa571a5ec5deb8bcbd3b