'File->Open Recent' entries open the wrong file when running 2 or more instances of JMeter at the same time

@stubarlow ([Bug 62282](https://bz.apache.org/bugzilla//show_bug.cgi?id=62282&redirect=false)):
I see unusual behaviour when opening tests via the JMeter GUI.

I often run multiple instances of the GUI on the same machine when executing smoke screen tests after a fresh deployment of the application I am testing.

If I open JMeter instances A and B and load tests A and B in that order.
Then go to JMeter instance A and open the first entry from the Open Recent list. The first entry says 'Test A' but what appears in the GUI is actually Test B.

Until now I didn't pay much attention to what appears in the left pane. Eager to find new defects in the application I test, I would just 'open recent' and then hit the start button. Because of this behaviour, unbeknownst to me I had the same test running in parallel in a few different JMeter instances and my test data exhausted a lot faster than I expected! :)

Severity: normal
OS: All