[graph-streaming] Graph remains locked when the http server is started

[panisson]

Branch: graph-streaming

It happens when the master is started with a non-empty graph in the workspace. The graph remains locked, and calls to graph update remain blocked.
Gephi Forum reference: https://forum.gephi.org/viewtopic.php?f=5&t=1642&start=0

[panisson]

According to the forum messages, this issue was corrected with the last commit