Fixed enclosing transaction is closed error

[xdev-developer]

Fixed enclosing transaction is closed error when multiple threads interact with graph.
Fixes #422

[janusgraph-bot]

Committer of one or more commits is not listed as a CLA signer, either individual or as a member of an organization.

[mbrukman]

@xdev-developer – the issue here is that the email used in your PR does not match the email used in your CLA.

No need to drop the PR; you can re-open it and solve this issue as follows:

• update your commit in-place as per these instructions to use the email address in your CLA and then update your branch and this PR via git push -f, OR
• update your CLA to change your email address if you changed your mind and plan to use this address going forward (we prefer you choose and stick with one email address though)

[mbrukman]

I see you opened PR #490 instead; that's fine too, but just wanted to note that you can also fix these minor issues in-place which avoids duplicate PRs for the same fix.

[xdev-developer]

ok, sorry, thank you!