[boltdb] testcase failed

[hsinhoyeh]

i got the following message when I tried to run test on store/boltdb

--- FAIL: TestMultiplePersistConnection (0.00s)
        Error Trace:    boltdb_test.go:69
        Error:          An error is expected but got nil. %s

turns out the underlying FcntlFlock implementation has been changed (boltdb/bolt@ebe3101) and boltdb also removed the corresponding test cases (boltdb/bolt@b9eb643), so I am not sure whether this testcase is still necessary?

[abronan]

/cc @sanimej