fuse: fix deadlock in TestDeleteNotify

This

	GOMAXPROCS=1 go test -v -count=1 -run TestDeleteNotify ./fuse/test

deadlocked reliably, apparently in the chdir() from cmd.Start().

We can do without the chdir() by using an absolte path.
This avoids the issue.

Fixes https://github.com/hanwen/go-fuse/issues/261

Change-Id: Ia9c8f15819c125c5bf94b085fa4c5f2977a6789a

fuse/test/delete_linux_test.go

@@ -81,8 +81,7 @@ func TestDeleteNotify(t *testing.T) {
 		return
 	}
 	buf := bytes.Buffer{}
-	cmd := exec.Command("/usr/bin/tail", "-f", "testfile")
-	cmd.Dir = mnt + "/testdir"
+	cmd := exec.Command("/usr/bin/tail", "-f", mnt+"/testdir/testfile")
 	cmd.Stdin = &buf
 	cmd.Stdout = &bytes.Buffer{}
 	cmd.Stderr = os.Stderr