tree bfccd1945c2acd6a1e987856893e427d663f79a9
parent 13922e34a96e0247424e197cfdf7121a6ea1c84f
author Sergey Rogulenko <rogulenko@google.com> 1432091418 -0700
committer Sergey Rogulenko <rogulenko@google.com> 1432091420 -0700

store/leveldb: adding mutexes

Wrapping db, snapshot and transaction with mutexes,
adding a bunch of tests.

This change also removes verrors from internal storage engine
for consistency: we should either use verrors everywhere or not
use them at all. As discussed with Adam offline, we should
probably start from the latter and switch to verrors later.

Change-Id: I38bf9760b35c40943225629c37e7d41ec8c30085