[foreign-memaccess] 8228584: DefaultModules test fails with incubating modules

[Maurizio Cimadamore]

Hi,
this is a quick patch to fix a test failure that is caused by the fact 
that jdk.incubator.foreign is an incubating module and, as such is non 
resolvable by default.

The test has a comment that, eventually, the test should check about the 
resolve status of a given module. In the short term we can simply filter 
out all modules whose name start with "jdk.incubator." which is a 
standard prefix for incubating modules defined in JEP 11.

Webrev:

http://cr.openjdk.java.net/~mcimadamore/panama/8228584/

Maurizio