RFR 8200355: local variable inference regression test generates classfile in test folder

[Maurizio Cimadamore]

Hi,
as the subject says, as a result of the tweaks done under JDK-8199910, 
the local variable inference test is generating spurious classfiles in 
the test/ folder. I've fixed the test to use jtreg's scratch dir as 
output folder for the file manager.

Webrev:
http://cr.openjdk.java.net/~mcimadamore/8200355/

Thanks
Maurizio