intel: When AUB dumping, flush before emitting final bitmap command.

intel: When AUB dumping, flush before emitting final bitmap command.

When we are generating an AUB dump, we make a final call to
aub_dump_bmp() as the context is being destroyed, to ensure that any
rendering performed before the application exits can be seen during a
simulation run.  However, we were doing this before flushing the batch
buffer; as a result simulation runs would not always see the effect of
all rendering commands.

This patch flushes the batch buffer just before making the final call
to aub_dump_bmp(), to ensure that all rendering is properly captured
in the final bitmap.