[reSIProcate] about berkeley db thread safe

[hongsion]

Hi,
	I found in repro Berkeley db is only used in single thread mode, to
use it in concurrent mode we have to initialize an environment for it. So I
think now repro's Store is not thread safe even using Berkeley db. Also we
found mysql connection will disconnect after long time no operation. So
there should be some work to keep alive for mysql connection in repro's
store. And I have a question why not use sqlite in repro.

Regards,
hongsion