Parallel client tests (#2890)

* alloc_runner

* Random tests

* parallel task_runner and no exec compatible check

* Parallel client

* Fail fast and use random ports

* Fix docker port mapping

* Make concurrent pull less timing dependant

* up parallel

* Fixes

* don't build chroots in parallel on travis

* Reduce parallelism on travis with lxc/rkt

* make java test app not run forever

* drop parallelism a little

* use docker ports that are out of the os's ephemeral port range

* Limit even more on travis

* rkt deadline

client/driver/test-resources/java/Hello.java

@@ -1,12 +1,14 @@
 public class Hello {
 	public static void main(String[] args) {
-		while (true) {
-			System.out.println("Hello");
-			try {
-				Thread.sleep(1000); //1000 milliseconds is one second.
-			} catch(InterruptedException ex) {
-				Thread.currentThread().interrupt();
-			}
-		}
+        System.out.println("Hello");
+        int seconds = 5;
+        if (args.length != 0) {
+            seconds = Integer.parseInt(args[0]);
+        }
+        try {
+            Thread.sleep(1000*seconds); //1000 milliseconds is one second.
+        } catch(InterruptedException ex) {
+            Thread.currentThread().interrupt();
+        }
 	}
 }