resatpi: Eliminate Exceptions in Mapper Tests

Up until now, mapper tests silently ignored several failures to
instantiated new objects using reflection. There were two types of problems:

- Instantiation of objects with no empty constructor (namely XMLGregorianCalendar)
- Mismatch between plural and singular entity name, e.g:
  'Floppies.java' vs 'Floppy.java' (differenct than truncating the suffix 's')

All exceptional cases have been handled in this patch, and all methods that
had a try/catch clause, which swallowed the exception, were made to 'throw'
the exception onward instead.

Change-Id: I84cabed0ff38196d8fd57d2f72ffdfe213f2ffed
Signed-off-by: Ori Liel <oliel@redhat.com>