fix race condition causing bodi to throw exception

[HuiSou]

Hi Everyone!

I've use this plugin with my test that contains around 14 testcases with multiple service registered ( Page object model, mostly) the plugin works fine with serquential execution but in parallelization, it failed with this signature after dozen hour of debug, I discovered that the static method without lock is a problem so after I change it and run for a while, the problem seems to be gone.

I'm not sure that you can release this fix on v3.9 or not, but that would be cool as I will not need a clone of your code in my repo.

Cheers!