Leave transition hook is called twice if css:false in in-out mode

[nkovacs]

Ran into this after trying your suggestion from #1241:

http://jsfiddle.net/nkovacs/a29fk09w/

[nkovacs]

Why did you close this?

[yyx990803]

Thought this was related to https://github.com/yyx990803/vue/pull/1246 ?

[nkovacs]

No, that didn't fix this bug unfortunately.