You can still destroy and get the stuff from container if it has {Lock:"PASSWORD"} tag.

I was messing around in my snapshot (survival) server with my friends, and then I locked my chest with command so my friend would not steal my stuff.

Well because he is very dumb smart I mean... he broke my chest and got my stuff.

It is cool that chests got new locking feature but it's pretty much useless because this annoying bug.
Please just make it that people won't steal some stuff from chests in public 1.8 servers. Thank you.