Always creates new pool in call em()

[alu]

@ivanceras Hi!

Pool::em() calls ensure(), so it calls init_pool always finally for now.
I thinks it's not necessary and happens problems sometime maybe.

[ivanceras]

Hi @alu , this looks like an oversight on my part. I haven't trace up when exactly a lot of the ensure() calls was introduced. Feel free to experiment by removing/minimizing the call of ensure(). I will get back on this when I have some other time.