Replace class with struct, since BJobStateListener is previously declared
as a struct in Job.h
Pointed by clang [-Wmismatched-tags]
Change-Id: I75293b48bcb521d25e98702d1fc1e0ab1008d504
Reviewed-on: https://review.haiku-os.org/482
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
