RFR (XS): 8220409: [TESTBUG] jdk jtreg test jdk/modules/scenarios/overlappingpackages/OverlappingPackagesTest.java - testOverlapWithBaseModule tests the wrong thing

[Langer, Christoph]

Hi,

please review this small test fix.

Bug: https://bugs.openjdk.java.net/browse/JDK-8220409
Webrev: http://cr.openjdk.java.net/~clanger/webrevs/8220409.0/

The test uses a wrong option "-add-modules" instead of "--add-modules" in one 
place.

Thanks
Christoph