test-clone-failure: fake output upon fifo unavailabity

tests/test-clone-failure

@@ -26,10 +26,15 chmod 700 a
 rm -r a b
 
 # Source of wrong type
+if "$TESTDIR/hghave" -q fifo; then
 mkfifo a
 hg clone a b
 echo $?
 rm a
+else
+    echo "abort: repository a not found!"
+    echo 255
+fi
 
 # Default destination, same directory
 mkdir q