Package certificate SecurityErrors triggered by MODULES-192

With WildFly 9.0.0.alpha 1, the MS SQL JDBC driver may fail to load due to inconsistencies in the signing certificates for the package. All classes are signed, but ClassLoader.checkCerts() sometimes does not get given them.

The problem appears to occur when multiple threads are loading classes from the package, and more classes have no certificates and fewer have them set.

Reverting the MODULES-192 change makes the problem go away, but I'm unsure as to whether it's a bug in that change or the change triggered a bug elsewhere