qa: add snaptest-estale.sh

Verify requests withing snapped namespace are directed to the proper
MDS.  We should never get ESTALE, only ENOENT.

qa/workunits/snaptest-estale.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+mkdir .snap/foo
+
+echo "We want ENOENT, not ESTALE, here."
+for f in `seq 1 100`
+do
+    stat .snap/foo/$f 2>&1 | grep 'No such file'
+done
+echo "Pass!"
+
+rmdir .snap/foo