RFR of JDK-8201469,test under java/rmi should be restricted to not run concurrently

[Hamlin Li]

would you please review the following patch?

bug: https://bugs.openjdk.java.net/browse/JDK-8201469

http://cr.openjdk.java.net/~mli/8201469/webrev.00/

( For othervm.dirs property, I just reformat it. )


In my test result, with jtreg option "-concurrency:4", after apply the 
patch, tier3 tests on different platforms will be slower about 1.5~2.0 
times than before.
I think stability of tests are more important than executing time, how 
do you think about it?

Thank you
-Hamlin