RFR(S): 8202289: Non-empty directory in module path is not handled properly at CDS/AppCDS dump time

[Calvin Cheung]

bug: https://bugs.openjdk.java.net/browse/JDK-8202289
webrev: http://cr.openjdk.java.net/~ccheung/8202289/webrev.00/

In ClassLoaderExt::process_module_table(), it adds all entries from the 
ModuleEntryTable with the "file:" protocol to the _module_path_entries 
and eventually to the _shared_path_table.
The FileMapInfo::check_nonempty_dir_in_shared_path_table() will check 
for non-empty directory in the module path.

Ran all CDS and AppCDS tests locally on linux-x64.
Will run hs-tier{1,2,3} tests.

thanks,
Calvin