Add shell based test harness

This allows you to simulate one or more simultaneously running mgmt
processes. It should be easy to use by following the test cases provided.

test/shell/t2.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+. etcd.sh	# start etcd as job # 1
+
+# run till completion
+timeout --kill-after=15s 10s ./mgmt run --file t2.yaml --converged-timeout=5 --no-watch &
+
+#jobs	# etcd is 1
+wait -n 2	# wait for mgmt to exit
+
+test -e /tmp/mgmt/f1
+test -e /tmp/mgmt/f2
+test -e /tmp/mgmt/f3
+test ! -e /tmp/mgmt/f4