SECURITY-769 AbstractServerLoginModule#validOptions

AbstractServerLoginModule#validOptions is initialized with the default
HashSet size (which is the default HashMap) size. However since it's
lazily initialized in addValidOptions and we have the valid module
options there we know what the right size will be.

 - change AbstractServerLoginModule#addValidOptions to initialize
   validOptions with the size of moduleValidOptions

Issue: SECURITY-769
https://issues.jboss.org/browse/SECURITY-769
Merge pull request #1 from marschall/SECURITY-769

Merged